Defender's Quest 2 March Update

Alrighty! Time for an update on where we are in Defender's Quest 2.

Those of you who follow me on twitter know I've been active, but I sometimes forget that our followers are spread out over multiple channels - our forum, our steam page, our gog page, our newsletter/website, our blog, etc. So, I'm going to try to shift from my "ignore everything but twitter" mode that I've unconsciously slipped into. From now on I'll try to supplement my daily twitter spew with decently-sized blog posts from time to time, and then link to them in all our forums, etc.

What We've Been Doing

First of all, until very recently we've been finishing up the last bits of legacy support for the original Defender's Quest. Now, you might ask, "Why would you spend all that time supporting an old game when you have a shiny new sequel to work on?" Several reasons:

1. It builds up sustainable long-term revenue
2. Our strategy is to slowly build DQ2 preorders over time to avoid Kickstarter-style pressure.
3. Send a clear signal that we really do support our games long-term

We have been doing some DQ2 work in the last few months, of course, but it's mostly been pre-production and part-time engine work. Lots of game mechanics and design depend on the story, and we wanted to give James (our writer) the proper amount of time to go through several drafts.

Oh, and my wife and I had our first baby (as did Anthony and his wife) about 8 months ago. So that's been a little bit of a time-sink :)

All that said, we have gotten plenty of stuff done and have some things to show. Alpha and Beta are still a ways off, and the official final release date is "When It's Done."


First I'm going to talk about the DQ1 legacy support we've been working on, then I'll get to the DQ2 stuff.

DQ1 Stuff

Six languages!

 

The biggest thing we've done for DQ1 legacy support is add five foreign language packs -- German, Japanese, Czech, Korean, and Russian. We contracted Fabian Bindel and Thomas Faust for our German translation, and worked with PLAYISM, a Japanese PC games publisher, for our Japanese translation. The japanese version just recently launched on their site (english page here).

The Czech, Korean and Russian translations were generously provided by awesome fan volunteers. (The Czech translation was provided by our own forum superstar 'coyot', the Korean translation was done by Team.SM, and the Russian translation by a large group of fans). It was a lot of work to get all these translations working, particularly when it came to user interface and font stuff, but we've learned a lot from the experience, and thanks to all that, DQ2's localization process will be a lot smoother.

In fact, we've already written the framework and released it under MIT license on Github, behold -- FireTongue! Like the rest of DQ2, it's written in Haxe, and is already being used in other cross-platform games, like this one! It was even featured in a brief talk at this year's GDC localization summit.

SteamOS, bugs, etc

We fixed a lot of bugs and  have been working on getting DQ1 running on SteamOS ever since we attended Steam Dev Days. Since DQ1 is still stuck with Adobe AIR, this is not an easy task. Although we have a good solution for regular Linux distributions (Ubuntu, Mint, etc), SteamOS is harder to get working. The difference is that SteamOS has a unique default setup that changes how the default user interacts with commands like sudo.

It's easy enough to work around it on my SteamBox by messing with the configuration, but we need to create a simple script that will work flawlessly for any user using only default factory settings. Thanks to the heroic efforts of Alexander Sturm and the nice folks at Valve, we've finally figured it out, but it's not up and running *just* yet. As you can imagine, I can't wait to have all my tech running natively on Linux via Haxe rather than AIR, as I blogged about recently.

We also need to get a Linux build ready for GOG Linux. Given that the intersection of GOG players and Linux users are solidly unified in their hatred of Adobe AIR, this is more of a delicate communication problem for us to solve rather than a technical one, but we'll get it sorted out soon enough.

Thagomizing

Finally, I've been steadily looking for opportunities to chase DQ1's "Stegosaurus Tail." You can read the linked article to get the full story, but the short version is that we've made more money in the second year of release than in the first.

By relentlessly chasing down promotional opportunities, we can keep introducing brand new people to DQ1, keep the bank account afloat, and thanks to our silly mini-ARG update, let new players know about DQ2 and drive pre-orders. Maintaining DQ1 sales is important because we don't want to rely entirely on pre-order revenue; the entire purpose of running a low-key "anti-kickstarter" is to avoid the intense pressure and hype usually associated with traditional crowdfunding drives.

FUN FACT: in the aftermath of writing the aforementioned article, I learned that the proper scientific term for the spiky bit of a stegosaurus tail is a "Thagomizer", originally coined by Gary Larson in a Far Side cartoon, and has since been officially adopted by paleontologists!

So from now on, I'm using the verb "to thagomize" to refer to the act of pursuing promotional opportunities for an old video game in order to drive further sales spikes on the long tail. 

"What you been up to lately?"
"Oh, the usual - coding, blogging, thagomizing."

DQ2 Stuff

Okay, so you probably want to hear about all the DQ2 stuff we've been doing!
Before I go any further, allow me to properly deflate your expectations with a metaphor.

The Iceberg Effect

Here's a picture of an iceberg. Notice that almost all of it is under water, and only a tiny bit pokes above the surface:

Via Wikipedia (source)
Uwe Kils (iceberg) and Wiska Bodo (sky).

A lot of work goes into making a video game, but the only part you can really experience as a player is the bit that pokes above the surface of the water. You see the graphics, the audio, the controls, but you can't see the thousands of lines of code behind the surface that keep the whole structure in order. And even if you could, you couldn't see all the planning, discussion, communication, etc.

When you're watching a game in development, what you're going to see is a whole lot of nothing for a long time, and then suddenly it will seem as if there's a sudden flurry of activity close to the end as stuff finally starts to poke up above the water line.

Only a few of you were following us back in DQ1 pre-alpha days, and absolutely nobody was following us for the whole first year of its development. For most of you (especially post-Steam), DQ1 just arrived fully-formed without having to wait for anything. So, please understand that "visual progress" is a really terrible metric for actual progress.

With all that said, here's what we've go to show for ourselves so far.

Arts!

Karen Petrasko has been working on some new concept art! Here's what the inside of a domed city might look like (click for hi-res mockup):

You can expect the same level of detail/visual fidelity in our battles, though I doubt very many will take place inside of a town. The above is more likely to be used in our in-engine cutscenes for when our characters are in a domed city.

And here's some random bits of concept art:


Top: Domed city exterior and interior Bottom: Emperor, soldiers, scavengers exploring the surface.

Here's a sketch of what our overworld map might look like:

And here's a new character we've been working on, who just goes by the name "Smug Captain" for now:

Dean Dodrill is still on board for this project, but he's had to take some time off to properly support/thagomize his last project, Dust: An Elysian Tail, and recover from a brutal, multi-year development slog. So we don't have any animations to show just yet, but we'll let you know when we do.

Musics!

Meanwhile, Kevin has been working on some of our first music tracks, which you can listen to here:

Defender's Quest 2 concept piece (mp3)
"Enemy City" WIP piece (mp3)
Untitled WIP piece (mp3)

Kevin wants me to SUPER EMPHASIZE that NONE OF THIS IS FINAL, it's all very early/rough work, and it will almost certainly change before the game hits final release.

Programmings!

We've made a lot of progress porting the Defender's Quest engine (known internally as the "TDRPG Engine") over to Haxe/OpenFL. I'm a big fan of open source development, so I'm releasing whatever bits I can as open source, under the MIT license. Since I started doing this, I've been officially accepted as a regular contributor to the HaxeFlixel project, and two of my libraries have been officially adopted into HaxeFlixel itself. The TDRPG engine itself remains private, but I like spinning off little bits of it wherever it makes sense to do so.

My most notable contributions include:

1. flixel-ui: a GUI library made entirely of flixel-native widgets, so you can intermingle them with other flixel objects, rather than awkwardly overlay a UI pane over your flixel canvas. This started by porting over legacy DQ1 code, but has since been massively improved. It's also easy to integrate with firetongue, so automatically making buttons twice as big in German mode is easy!
   
   

   

   This is just a demo -- DQ2 will look much better

   Defender's Quest has an enormous amount of interface, so this and the battle engine represent the bulk of the coding work.
2. flixel-editors: a set of editing tools for flixel. Right now it only has my "Animator" tool, but it should have more stuff soon enough.
   
   

   

   The Animator tool is not for building animations from scratch, but rather for previewing spritesheets in-engine, and building individual animation sets out of frame indeces. It also lets you set "sweet spots" to define where projectiles (for example) should originate in an attack animation, and various other features.
   
   It also comes with built-in support for re-coloring both pixel-based and "HD style" sprites. In the screenshot you can see an example of the latter -- I'm using a sprite from Glitch to test with for now while we work on getting more our own stuff ready.
   
   It's important for us to know what the basic limitations of our tech is so it also has the ability to run rudimentary stress tests. We'll need better benchmarks to really know where the boundaries are, but initial results seem promising, and way better than what DQ1 could handle:
   
   
   We plan on having a cutscene and level editor eventually, too. I haven't decided yet whether those should be open-source, too, but I'm leaning towards it.
   
   Why am I spending so much time with tools and stuff?
   
   50-75% of DQ1's development time was CONTENT CREATION, and LOTS of time was wasted manually processing/integrating content with bare-bones tools (text editors and photoshop, basically).
3. firetongue: my localization framework. Originally ported from DQ1 code, but massively improved.
4. flixel-demos: I didn't create this repository, which showcases various flixel features, but I did contribute these individual demos: cursor, heatmap pathfinding, blend modes, rpg interface, file browse (Note: file browse has to be compiled on native targets to see its full functionality). All of these demos are the result of me testing features we needed for DQ2.
   
   
   

For the rest of my stuff you can see my github profile or open source report card.

NOTE: this is open-source development, so all "my" stuff has received lots of bugfixes and improvements from the HaxeFlixel community, for which I am very grateful.

What's Next?

So there's still a lot of work to be done. I really need to dig into the new battle system engine, and story material is starting to mature. Then we can draw on that for a few story announcements, we can get art from that, get music from that, etc, and roll that all back into the design.

When will Alpha be? I hope to have something playable before the first half of the year is over, but no promises.

Other stuff we're looking into is whether it's worth it or not to plan for a console release. Now, there's no chance we'd be interested in from-scratch ports, so everything depends on us being able to get the Haxe/OpenFL stack working for those systems. In theory, it's possible, it's just a matter of building out the native targets. So far we've made some good progress using HTML5 (believe it or not) for the WiiU's Nintendo Web Framework, but what we'd really like is truly native support on everything, especially the 3DS and PS3/4. We're putting little feelers out and seeing if we can find the right people for this, because I sure as heck can't build it myself. So far we have some promising leads but we can't announce any of that just yet. Let's just say I'm not regretting switching to Haxe.

And in any case, our top priority is getting the game running on Windows/Mac/Linux. If -- and I do emphasize "IF" -- we release on console, we will make sure that is most certainly not at the expense of PC development.

The Stegosaurus Tail: when "The Long Tail" grows spikes.

You may have heard of "The Long Tail." For games, it means your sales start off strong and quickly taper off.  This force drives the retail marketing cycle -- launch a game to extreme hype, sell it like crazy, then immediately abandon it and move on to the next thing.

The Long Tail

Chris Anderson's book, The Long Tail: Why the Future of Business is Selling Less of More notes that given enough time, the "long tail" (the yellow part of the graph) can reach or exceed the size of the initial spike (the green part).

Basically, if you reduce the cost of inventory and distribution, there's as much money to be made from selling an ocean of niche products by the drop as there is in selling big hits by the boatload. This strategy is at the heart of industry titans like Amazon, Netflix, and Steam.
Of course, that strategy is reserved for big content aggregators who make their money regardless of whether any specific product does well. But can individual developers take advantage of the long tail, too? Bennet Foddy thinks so: in his GDC Talk, Learning to QWOPerate, he talks about how he self-published many small games on his site and used them to cross-promote one another. Eventually he stacked up all the long tails and made sustainable advertising revenue.

The Stegosaurus Tail

 

It's hard for me to take advantage of Foddy's method because I don't make lots of small games one
after another -- it would take me years to build up a back catalog at the level of polish and scope I'm used to.  So for now all I've got is one commercial title - Defender's Quest. And if all Defender's Quest's got was a Long Tail, I'd be screwed. Instead, it grew spikes and became a Stegosaurus Tail.

That's a chart* of our lifetime daily sales revenue over nearly two years. The far left side of the curve resembles the "Long Tail" -- a large initial spike quickly tapering off. But even this spike is noisy - as noted in Defender's Quest: By the Numbers, part 1, sales initially spiked with press coverage, then again when our demo was featured on Kongregate and Newgrounds. We had a few more small spikes from our big, free, "Gold Edition" update, but nothing major until our launch on Steam and GOG -- which brings us to where where we were at in Defender's Quest: By the Numbers, part 2.

But after that, we had the Steam Linux Sale, various GOG promotions, and another huge surge when we launched our Steam Workshop support. Spike after spike, often several months apart.

*Parenthetical: why distort the stats?

In previous sales articles I gave detailed sales stats, including per-platform revenue breakdowns, but recent changes in the terms of service with some of our distribution partners forbid me from doing so again. The sales chart is thus intentionally fudged -- our real chart has the same overall shape but the exact daily sales are arbitrarily different.

The portal(s) said they changed the rules because they have to keep developers' sales data confidential. So, in theory we could publish detailed stats, but people on the internet are too good at math -- they can combine those stats with sales chart positions to estimate another developer's confidential figures, and portals are afraid to indirectly expose another developer's confidential sales stats. I *am* still allowed to publish total PC sales stats across all channels mixed together, but I'm choosing not to do so at this time.

Implications

I suspect most games on Steam and similar portals have stegosaurus-tail sales charts -- for instance, here's the sales chart for Garry's Mod:

But so what? How does this change the game?

Well, first of all...

Long-term support can actually pay off!

Under the Long Tail, the post-release sales strategy is to abandon your game. Give it just enough post-launch support while it's still selling strong, then move on to your next project.
We took a different approach. Instead of immediately moving on to Defender's Quest II we put a lot of time into bug-fixes, patches, and content updates. Our biggest patch, "Gold Edition," upgraded our art style added New Game+ mode, and lots more. This was a gamble, improving the game to catch Steam's attention, and fortunately, it paid off (this was before greenlight). From that point on we looked for every opportunity to turn a content update into an excuse for a partner to promote the game. Examples include the Steam Linux launch and our Steam Workshop sale - the latter being one of our largest spikes ever. We've also had a lot of success in getting promotions from GOG.com.
But before you go off and spend a lot of time and money on a content update, it's best to get your distribution partner to agree to a promotion ahead of time, in writing.
The next implication is...

Don't compete on price!

When Defender's Quest first launched, the full price was $7. When we launched the Gold Edition upgrade, we raised the price to $10, and finally settled at $15 after launching on Steam. However, the game's full price is essentially a fiction -- you can see from the chart (and our previous articles) that pretty much all the revenue comes during promotional periods when the game is on sale. The full price is therefore just how much room you're giving yourself to go down during promotions.
Accordingly, here's an interesting stat - while the full price has increased over time, the average price per purchase has remained about the same. All that's really changed is how deep we can make our discounts. In a perfect world I'd just keep the same medium price all the time, but that's just not how human psychology works.
Developers often worry that players will complain about a higher price, but it's important to remember those players can always trade money-dollars for time-dollars by waiting for a sale. (You can see this process play out in this thread on our steam forum).

But temporary discounts won't do much by themselves - you also need...

Promotion!

"Sell your game for less and make up for it in volume" says conventional wisdom, but this only works if you can actually count on that volume to actually show up and notice that your game's on sale. The persuasive power of the promotion drives the sale, not the mere fact that it's discounted. For instance, Democracy 3 was Positech's fastest-selling game ever, even though it released at full price without the customary launch discount. Promotion drove those sales, not pricing.

Ever heard of Monroe's Motivated Sequence? It's a rhetorical structure from Communication theory, and if you've ever watched an infomercial you'll recognize it: attention --> need --> satisfaction --> visualization --> call-to-action. In other words, basic salesmanship. Take it away, Rhett & Link:

Video game sales promotions, be they Steam Sales, GOG Sales, Humble Bundles, etc, loosely follow this structure. They get your attention, show off cool games you've been waiting to play, give you lots of visuals, info, demos, and a ticking clock that presses you to act now!

This is nothing new - department and grocery stores have been doing this since the late Cretaceous, and I'm surprised it's taken the games industry this long to evolve beyond the "launch at Full Price, then chuck it in the Bargain Bin" cycle I grew up with. Promotions give games a second wind.

I define a promotion as strong consumer attention combined with a strong call-to-action. It's not just any attention. For instance, new developers often think exposure from a great review will make them rich, but I can say from experience it won't. Some articles have given us modest sales spikes, sure, but just as often we've had glowing write-ups that didn't even move the needle.  And that's fine -- critical acclaim and financial success have never been joined at the hip, nor should they be. But if you're looking for raw sales, it's promotions you want. And the best promotions are front-page attention from a major distributor.

So, if you're looking to add spikes to your stegosaurus tail...

Get real friendly with your distributors!

Ideally, the relationship between developer and distributor is symbiotic -- the distributor gets a cut of your revenue, you get access to their audience, players get awesome games at great prices, and everybody wins -- ideally. This assumes that your distributor is benevolent, or as Daniel Cook would say, in the "Engage" phase of the Game of Platform Power (more on this later).

But even if your distributor is on the side of the angels, it's still easy to get lost in their roster of other developers. "The squeaky wheel get the grease," as the saying goes -- if you don't ask for a promotion, you won't get it, and the only one advocating for your game is you. We talk to our distributors every time we start working on a content update, and we check in weeks or months ahead of every seasonal sale to make sure they don't forget us. Also, we frequently volunteer whenever our distributors roll out a new feature or promotional campaign.
And as long as our interests align, I'm happy to do little favors here and there. For instance, I'm a big fan of GOG.com, so I've done several promos for them to help them reach out to other indie game developers. Another example is Kongregate, who promoted our game when we added an in-game incentive for anonymous users to sign up for Kongregate accounts. Now, I'm not advocating for being a corporate sell-out or an amoral shill ready to do every horrible thing in the book just to get revenues. I'm just saying that in ideal circumstances, your distributor relationship is a true partnership -- you help them, they help you, and everybody wins.

All that said, it's important to remain vigilant because even the nicest portal today could turn to the dark side tomorrow, or the "Extract Phase," as Dan C. would put it. It happened with Big Fish Games in the casual market when they slashed developer revenue share, it happened with Apple and Facebook, and it tends to happen with console generations once they start to mature. The thing to look out for is "Rent-Seeking Behavior." Now, as above-board and transparent as companies like Valve are, nobody knows the future. Gabe Newell could always get struck by lightning, and an evil hedge fund could seize control of Valve and clean house. Wills can be and often are flagrantly ignored if the estate is valuable enough. As Moxie Marlinspike would say, it's not about trust, it's about trust agility.
So those are a few ways the Stegosaurus Tail phenomenon changes the post-release game plan. But if you look closely at history, Steggy has been with us all along.

The Stegosaurus Tail's Legacy

Some game companies have already been "riding the dinosaur" for decades, most notably Nintendo. Back in the 90's when other publishers would routinely consign their back-catalogs to obscurity as soon as their games were off store shelves, Nintendo never stopped coming up with new ways to re-sell us classics like Mario, Zelda, and Metroid.
GOG.com has been doing the same thing with classic PC games for years -- taking old abandonware gems, polishing them up, and giving them a new lease on life. Major publishers have since joined in and even Steam has joined the party, most notably with System Shock 2.
What's really cool, though, is Steggy's power to re-write history. Double Fine's Psychonauts was a critical classic but a financial flop, until it was re-released on PC many years later and finally got its chance to shine in the light of Steam Sales and Humble Bundles.
What works for the big boys can also work for us small developers -- if you're able to release multiple games, you can use them to drive interest in one another, giving your back catalog a kick every time you come out with something new. For instance, Zeboyd games sells Breath of Death VII and Cthulhu Saves the World as a double-pack, and included these and other games of theirs as backer rewards for Cosmic Star Heroine's Kickstarter campaign.

We've been doing the same thing -- Defender's Quest 1 now comes free with every pre-order of Defender's Quest 2, and we've updated the original game with a free in-game item for those who visit the Defender's Quest 2 page. Since we added that feature, not only do DefQ2 preorders closely track DefQ1 sales, daily DefQ2 preorder revenue exceeds daily DefQ1 sales revenue.

We still have a few tricks up our sleeve to add a few final spikes to our tail. When we first launched, nearly all of our direct revenue was driven by referral traffic from our web demo hosted on Kongregate and Newgrounds, so we're in touch with both of those sites about future promotions. Also, we'll soon be launching a Japanese translation as part of our new partnership with Playism, distributors of awesome Japanese indie games like La-Mulana and One-Way Heroics, and a German translation should go out any day now.

The Uncertain Future

There's some downside to maintaining a Stegosaurus Tail -- it's hard, boring, work. What I love doing best is making games, and although every new spike I successfully chase down feeds my family and keeps my career afloat, it also distracts me from pouring my soul into my next project. After over a year of nurturing her, Steggy's starting to wear me out.

And before I close, I want to note that no single strategy works for everyone, nor does it work forever. Much has changed since Defender's Quest first launched -- back then, Steam was hard to get into, but easy to get noticed on. Today, with indie games literally being greenlit by the hundreds, it looks like the future will be the reverse. Maybe Steam will follow my predictions and solve discoverability in a way that's both sane and equitable, but that's far from certain. Furthermore, the long-term effects of Steam-style promotions is unknown. With players building up huge backlogs, will they keep buying new games like they used to?

With the ground shifting underneath us, and amidst all this talk of an "Indie Bubble," I think it's best to double down on the fundamentals -- sell direct, know your audience, make sure they know you, diversify your sales channels, and if you've got a back catalog, milk it for all it's worth.
The last lesson I've learned is this -- a great game is not disposable. Just like a little kid watching Star Wars for the first time, someone out there is waiting for your awesome game to captivate them, they just don't know it yet.

Indie RPG's on sale TODAY

So, the Because we May sale just launched today, and about 180 or so games are participating.

I'd like to direct your attention to a select few of those that might pique your interest.

Indie RPG's!

Of course, you should definitely check out our own game - Defender's Quest, which is available during the sale for the low, low price of just $2.99 - your best opportunity to get the game and your right to free updates before our upcoming "Gold Edition" expansion is released.

The Indie RPG crowd is pretty tight-knit. There's not all that many of us, and so we like to help each other out.  Robert Boyd and Jay Barnson were kind enough to write about us when we first got started, and today I'd like to return the favor and "pay it forward" as it were, to other amazing Indie RPG's out there that need some love. Also since you liked our game, you just might like some of these, too.

No one's paying us anything to list these (I generally hate ads and won't accept them on this blog) - all of these are here because I find the game interesting and would like to pass on the news to you :) 

Also, you won't find this many low prices on Indie RPG's all in one place for quite some time!

To help you make up your mind, I've collected two reviews for each game.

Frayed Knights: The Skull of S'makh Daon

 $9.95 (was $22.95)

Reviewed by: IndieRPGs, RPGWatch

Telepath RPG: Servants of God

$14.95 (was $24.95)

Reviewed by: Did-Not-Finish, The Indie Mine

Avadon: The Black Fortress

$4.99 (was $20.00)

Reviewed by: GameSpot, Zeboyd Games

Squids

$3.99 (was $6.99)

Reviewed by: TouchArcade, Gamezebo

Cardinal Quest

$2.00 (was $5.00)

Reviewed by: TruePCGaming, IndieGameMag

Cthulhu Saves the World + 

Breath of Death VII Double Pack

$1.49 (was $2.99)

Reviewed by: IGN, Rock, Paper, Shotgun

Dungeons of Dredmor

$2.49 (was $4.99)
Reviewed by: IGN, Bit-Gamer

I think that's enough for now :) I might add more to the list as the week goes on. Be sure to spread the word to all your friends and enjoy all these awesome games!

(To the developers: the images above are hotlinked directly from your sites because that was the easiest thing I could throw together in 5 minutes, and I figured you wouldn't mind since I'm promoting your game. If it's a problem, just let me know in the comments or shoot me an email and I will take the time to download the image to my own server to save you the bandwidth).

Quick News

Hey everybody! We've got a lot of awesome Defender's Quest news for you guys today!

First and foremost, we're making good progress on gold version.

Second, I'm pleased to announce that Defender's Quest will be featured in the upcoming Because We May sale, which starts tomorrow and will last through June 1st. During that week, Defender's Quest will be available for the low, low, price of just $2.99!

After the sale, the game goes back up to it's regular pre-release price of $6.99, and when gold edition comes out the price will go up to $9.99, so get your foot in the door now! Anyone who buys the game now will get free updates, which includes a free update to the gold edition.

So, here are the things that are new in Defender's Quest gold:

1) Awesome new art
2) Unique upgradeable loot
3) Magic books
4) Bonus battles
5) Sidequests
6) Mod support

I'll be posting some more details soon, but it's already 4 o'clock and I need to make sure this post actually gets done :)

So, first and foremost, click on the new picture of Slak to get a preview of our new awesome sprite art!

I'll be posting more stuff soon :) Thanks for following us!

Details on upcoming GOLD version

EDIT:
For everyone who's been asking, YES! If you have bought any version of the game so far, you will most definitely receive the GOLD edition as a FREE udpate. With Level Up Labs "Free Updates" does indeed mean free updates :)

Hey Defender's Quest fans!

Monday is when we will normally issue updates, if we have any ready. We don't have one this week because I've been busy working on gold features, which will be held back until they're all done and then released all at once.  When we do have udpates, though, rest assured, you'll see them on Monday :)

Also, Anthony's at GDC all week so it's just me and James holding the fort, so it might take a little longer to answer emails / respond to forum posts, etc.

So, with that all being said, let me tell you guys what we've been up to lately! Announcing...

Defender's Quest GOLD EDITION

Gold edition will be version 1.0 of the game, but we haven't definitively and clearly stated what will and won't be in the game.

Now that development is well under way, here's what we can commit to:

New Art!
Yes, we're giving the game a major face-lift! We're keeping the character designs mostly the same, but we're putting in all new backgrounds, new sprite animations, and depending on time and budget might overhaul  the UI and some other elements as well.

For digital painting stuff, we've hired the amazingly talented Karen Petrasko, who's worked for  Amaranth Games, PassionFruit Games, Wadjet Eye Games, Gamenauts, and others.

Here's the new title screen she did for us:

Here's another quick tease - the new "golden man enthroned" background:

We'll share some more art in the future as we get it done :) We also have some sprite artists, too, but we'll share more details on that once we get some stuff done at that front.

Note for those with art-style grumps:
If you're incredibly attached to our old art style for some reason, we'll consider an option to switch between the styles. This will require us to switch the way we load assets to the game, so we'll only do it if we have time, it's technically feasible, and enough people really, really want it.  Unlike last time, we will have two complete sets of art , so it's at least possible this go-round.

This would add the native ability to mod the art style for the game, so it'd have other uses as well, but we've got a ton on our plate already, so unless there's a lot of demand please understand that though it's doable, it's a bit low on our priority list.

More End-Game Bonus Battles
We'll be including more bonus battles for sure.  Right now we're leaning towards most of these being "epic" battles, ie, a fixed-wave challenge, such as 50 or 100 waves, with one or more "endless" challenges as the very last ones, so there's a natural progression to the list.  Haven't decided for sure yet, but basically - more bonus battles!

Doing Something With Unique Equipment
You'll notice you can't sell any of your unique equipment.  This is because we're doing something with it in Gold edition - we're not sure just what yet, though!  Basically, I want there to be some mechanism for upgrading these items into "super" versions that are viable end-game choices. What exactly that means though is still TBD.


New Game PLUS
A common feature in JRPG's is a "New Game+" mode where you can start a new game using the data from a save slot that's already beaten the game, and experience some new features.  Chrono Trigger famously did this, letting you retain all your experience and equipment to blaze through the game and experience some secret endings.

In Defender's Quest, all you have to do to enable NG+ mode is beat the game. Any challenge level will do, so even if you only eke by with blue stars on casual mode, you'll still get there.

When you beat the game, your save slot will look like this*:

After you've started a New Game+, it will look like this:

*Just a design mockup. Final look will depend on the new UI and sprite styling.

"Play" will take you to your normal save slot.  "Play+" will take you to your New Game+.  The data for NG+ works under a "two-slots in one" model.

Your party data is shared between the two worlds.  All levels, xp, equipment, scrap, skills, etc, gained in one will be exactly the same in the other.  Your map and battle progress in each world, however, is tracked separately.  Since party data is shared, when you start a NG+, Azra starts out at full strength with all her xp, levels, and spells.  You start with an empty party but whenever you encounter each hero, like Slak, Ketta, etc, that character class is unlocked in NG+ mode, and you'll now see all of your recruits from that class at their old powered-up strength with all their equipment and skills.

All of the battles will be given a face-lift for NG+ that raises the challenge.  We could have just bumped everything up by X levels, but that sounds boring.  However, creating new content for each and every challenge would be way too much work.  What we're doing instead is creating new monster types that only show up in NG+ mode, and creating a global replacement rule across the game.

That means, every monster in normal mode will have a corresponding "alternate" version in NG+, kind of like how in the original Super Mario Bros' "second quest" the turtles were replaced with fireproof buzzy beetles, which in turn were replaced by unstompable spikeys.  We'll also apply a global monster level bump of some sort, and that will be how we generate the new battle content for NG+.  Hopefully that will be a good amount of new and interesting content without too much extra work.

These new monster types will have new and interesting behaviors, not just rehashes of stats and existing abilities. What exactly those will be is still a secret, though :)

For boss battles we might manually hand-craft the NG+ versions of those, we haven't decided yet.  Battle rewards will probably be new, and there'll most likely be a new set of non-unique items in the game so you still have stuff to spend money on.

New Game+ will also raise the level cap, for obvious reasons :)

The next thing about New Game+ mode is that it will include some other special features. Namely...

Side Quests

We've identified natural places to insert new missions that run perpendicular to the normal story arc. These will inject a bit more story and gameplay content and generally add spice.  These battles will be special and do things like restrict which classes you can use and a few other surprises so they're not just "more battles" (because we already have lots of that with NG+)

So, first off - why are Side Quests only in NG+ mode? Why not also in normal mode? A few reasons:

1. Most of you have already beaten the normal game
   If we include sidequests in the normal quest, there's little point in playing them in the normal mode as you'll be way over-leveled.
   
2. We like the "core" story experience of normal mode
   Side quests tend to slow games down.  We feel normal mode has really good pacing and a driving central motivation pushing things forward.  We feel that in normal mode, the sidequests would be distracting to new players, but in NG+ where you've seen the old stuff already, these will be a nice new treat.
   
3. If it ain't broken...
   We've got a good thing going with normal mode, so in the unlikely event sidequests totally destroy the narrative, it only affects a special bonus mode and doesn't tarnish first impressions of the game.

These sidequests will reveal a little bit more of the backstory of Defender's Quest and also give us more chances for individual characterization, as well as cool new battle set-pieces. The next feature is related to this end...

Azra's Journal

Being a Librarian, Azra has been writing down her experience in the Pit.  In NG+ mode a prominent "Journal" button will be added to the UI which lets you read her thoughts:

New Journal entries will be added as you progress through the game, documenting Azra's observations and generally fleshing out the experience through details, notes, and sketches.  We're going to try to nail that "British Naturalist in the Galapagos" vibe.

So, what's the point of the journal? And why is it only in NG+?

1. Gives our writer something to do
   Most of the NG+ features are art and programming heavy, but this will keep James busy and will hopefully provide some content that people who love story will really be able to dig into.
   
2. Provide NG+ story rewards
   In normal mode, before and after every battle you get a little cutscene, which is a great little reward.  In NG+, you've seen all the cutscenes already (and yes, we'll add an option to auto-skip cutscenes) so the reward is diminished.  This should provide a new story reward for those who are into that.
   
3. PacingThe Journal is available only in NG+ mode for pacing reasons, again.  In normal mode, I would be afraid people would feel obligated to click on it every time it shows a new entry, and since normal mode has so many cutscenes already it'd be in serious danger of slowing the player down.
   

We might use the journal to provide basic info-dumps on in-game things, like an enemy bestiary, for example.  If we do that, we'd probably make those basic functions available in normal mode, but keep the extra story entries as exclusives for NG+.

So, those are some things we can formally announce for Defender's Quest Gold edition!

One last thing, because some people have asked?

Why Gold Edition? Why not a sequel?

Some people have asked why we're bothering with such a big update to the game rather than focusing on immediately doing a sequel. Some have mentioned that the updates might be of only marginal value in attracting new sales and that our time would be better spent making an all-new game for our existing fanbase.

There's several reasons we're doing GOLD edition:

1. This is the game we want to make
   This is the definitive version of Defender's Quest, and we would have finished it to this degree if we could have afforded to, but we had to release early to survive. Now that we're doing pretty good, we can afford to roll out these bonuses and make the game we're happy with.
   
2. We really want to get picked up by Steam/HIB, etcWe've submitted to Steam and the Humble Indie Bundle, but haven't heard back from either.  These added bonus features - in particular the new art style - will give us a better chance of being noticed. If we get picked up by either we could likely expand our audience by 10x at least.
   
3. We want to put our best foot forward for Desura/Impulse/GamersGate/IndieVania/etc
   Regardless of whether Steam/HIB come knocking, we're going to launch on the other big digital distribution portals, and we want to polish up the game a bit before then so that we can really drive sales on first impressions.
   
4. Attract another round of press attention
   Releasing a big update will hopefully get us some more reviews. By responding to all the criticisms we've seen so far, hopefully the next round of articles will be even better :)

Oh right, I forgot one last thing:

RELEASE DATE : When it's done.

We slipped on our original release date for early release, and we're not making that mistake twice. Our honest estimate is something like a month or two, but who knows.  Could be longer, could be shorter. 

We'll keep you posted.

-Lars out.

News! Calling for Testers!

Just sent this newsletter out today:

(REPLY TO: defendersquest@gmail.com)

Hey Defender's Quest fans!

First, thanks so much for being patient with us as we prepare for our preliminary "Beta Launch" this month, at a special discounted price of $6.99 ($4.99 for you newsletter subscribers!)

(We're getting very close - things are coming together and as we approach release we will send out frequent updates.)

Second, thanks to everyone who sent in their save files. We have waaaaaay more than we need at this point! You guys are awesome.

Third, thanks to everyone who sent us e-mails of encouragement and support. It's really great to hear from you, and nothing motivates us quite like hearing that you guys can't wait until our game comes out! Our only hope is to meet (and hopefully exceed) your expectations :)

Fourth, some people were wondering why they hadn't received a coupon code yet. We haven't sent them out yet :) Those will be sent over the newsletter at the same time as the Beta Launch.

Fifth, on to other business:

We don't have a specific date to announce just yet, but we can say that we're veeeery close. All that's left right now is bug-fixing, balancing, and plugging in art for a few cutscenes. To that end, we'd like to recruit some of you to help us test the game before we launch. If you want to VOLUNTEER to be a tester, send an email to defendersquest@gmail.com and put "TEST VOLUNTEER" in the subject line and we'll hook you up with the latest builds of the full version of the game.

NOTE FOR TESTERS:

Now, let me explain real quick - if you volunteer to test the game, you'll be seeing an incomplete version of it. If your motivation for testing is just to play the game sooner, I STRONGLY recommend just waiting until it comes out - testing games is not always fun. The final version will be much better than any unfinished test version we can provide you with right now.

If your motivation is to help us make the game better, and you don't mind braving bugs, unbalanced levels, and a few rough, unfinished, cutscenes, then by all means sign up! We appreciate anyone who volunteers their time and effort to help us make the game better.

So, here are some basic guidelines for being a tester. If we provide you with a test copy, you agree to:

1) NOT re-post it anywhere or otherwise share it with people
2) Thoroughly test the game and look for bugs, glitches, balance issues, etc.
3) Provide us with useful and detailed written test reports (we'll give you templates and instructions)
4) Give us complete permission to use any information, ideas, data, or anything else you share with us

The main things we're looking to discover through testing:

1) Obscure technical details -
Does the game work on old computers? Does it crash on Linux? Does it run slow on Mac? Does it fullscreen properly on a netbook? Does it break on dual monitor set-ups?

2) Bugs - when and where does it crash, break, or otherwise screw up?

3) Balance - let us know when and where the game throws you up against an insane difficulty wall or suddenly becomes way too easy.

Here's some things we're NOT looking for in testing, because it's way too late in the game to address now:

1) Cool ideas for new features
2) Revisions to the story
3) Art style changes

Thanks for everything! We'll be sending out more updates as we get closer to launch, so stay tuned! And of course, if you don't like getting these newsletters, feel free to unsubscribe using the link at the bottom.

Thanks,
Lars Doucet
Level Up Labs, LLC

New Art Style

Let's talk a bit about the new art style we've been trying out.  The biggest weakness we have right now is that the team doesn't have a dedicated artist.  I (Lars) consider myself a half-decent artist, but I've been so busy programming, blogging, running around putting out fires, etc, that I have very little time to dedicate to art at this stage of the project.  

We initially assumed that we could just get away with using me for both jobs, but that's something we won't be doing again.  Next project - dedicated artist for sure.  

So, a few weeks ago we took a good look at our art style and decided to make some changes.  Our goals:

1. Make something we're happy with

2. Create backgrounds that don't look like barf

3. Make the characters more expressive

Nothing good needs to be said about the old backgrounds. They're hideous, and they're all being replaced:

The old art style just clashed and was honestly something really thrown together while we focused on other parts of the game. The new style is simple, clean, and works well with the new character style.

As for the characters, the old art style was a collaboration between myself and our writer, James - he designed the characters and then I did some cleanup work, shading, etc. In the end, this not only took too much time, but had mediocre results (which I'll take the blame for).  Although I'm partial to the comic-book style with outlines and shading, it takes way too long, and is prone to errors when I'm rushing (if you look closesly, you'll find places where shadows are going in two different directions).  With a dedicated artist this wouldn't be a problem, but given our situation we decided a style without outlines and hard shading would be faster, mesh better with backgrounds, and easier to revise.

NOTE: We're not looking for an artist right now (at least not for this version of the game).  We've already had people offer to work for free - we appreciate the sentiment, but we won't hire someone without compensation, and right now we can't afford more team members.  If the game is successful, and we plan on a sequel or porting it to a new platform - then, definitely, send us your portfolios :)

For now, James is doing all the new art, with only a little bit of help from me, freeing me up to do a lot more programming and systems work.  So, let's take a look at some of the new stuff:

I wasn't really happy with Azra's proportions, hair-style, and expressions.  She also looked like a cross between an 8-year old and Kim Possible. We want good expressions to really sell the story, and the new art style frees us to do that.  The lack of outlines and hard shadows makes it easier to just get in there and change things in a few minutes without getting caught up in detail.  The previous style was very difficult to revise - so if we had a mediocre pose, we were more likely to stick with it rather than throw it away and start over.  That, and we can crank out a lot more unique poses for specific lines of dialogue, rather than just re-using the same three or four over and over again. 

Here's another cutscene from early in the game - I like the new background and characters a lot better. The textured paper makes it feel more like a story-book and meshes better with the character art than the old style.

All the characters have way more poses now, and the expressions are really great, the story feels like it's coming to life in a way that it didn't before.  

For those who complained about the scene with Ketta from before - that was the first scene we did in the new style, so we'll definitely be giving it another pass before shipping :)  Also, Ketta's new character design was inevitable regardless of art style, because a disturbingly large amount of testers didn't realize she was a woman, and in battle players had a hard time distinguishing her head icon from Slak's because they both had big red afro's. We'll post an updated version of that cutscene as soon as we polish it up, and hopefully it will address people's concerns that it wasn't expressive enough.  If not, oh well - we can't please everyone :)

We've also updated in-game dialogue, which looks way better and conveys a lot more emotion:

Anytime you change an art style this drastically, it comes with risk. I've already gotten a few negative comments by people who preferred the old style, for instance.  All I can really say about that is that I do appreciate any feedback we get, negative or positive, and I hope you guys understand that we'll do our best to address everyone's concerns, but ultimately we have to go with what we think is best for the game.  Also, the little snap-shots I put out aren't always going to be indicative of what you see in the final version of the game, so we'll keep changing/polishing right up to the end.

We WILL be releasing a new version of the demo to coincide with our "Beta" launch, so you'll be able to see how it looks AND plays before deciding to buy.

We hope you like it! And if not, we hope you at least still like the game :)  I'll be posting shortly about all the super cool amazing awesome stuff we've been up to.

I think you're really going to like Acts III-VII, and if I may say so myself, the final battle is pretty cool. We've been giving it a lot of special attention.

News!

Sent this newsletter out today.  If you're not currently getting the newsletter, consider signing up! If you do, you'll get a coupon code good for a nice discount when Defender's Quest is released!

On to ze newsletter:

Hey everyone!

It's been a while since our last newsletter, and we've got lots of exciting news about Defender's Quest! 

Since we released our initial demo, we've gotten lots of great feedback. We've been working furiously ever since to address as many of the issues people raised as possible. Among countless tweaks to gameplay, balance, skills, and other features, we've also given the game a significant graphical overhaul - user interface has been improved throughout the game, and we have a brand new art style for the cutscenes (which was the #1 complaint from the demo). The public demo was updated a while ago to reflect some of the new UI changes, but you won't see the new cutscene art until release.

Here's a sneak peak at some of the new art updates, old on the left, new on the right, click to make big: 

Cutscene Art (click to make big)

Recruiting Interface   (click for big)

Battle Preview Interface   (click for big)

While all this has pushed back the release date a tiny bit, we want to stick as closely to our original goal as possible, and are now aiming for early December. 

Here's the current plan:

*********************
Early December 2011 
Initial release 
$6.99 USD 
*********************

This will be a "beta" release. This will include the full, playable game with all the story, but might have a few bugs and will be lacking some extra bonus features we plan to add later.

The beta release will cost $6.99 USD. Everyone who purchases this release will get free updates and an upgrade to the full version when it comes out. Once the full version comes out, it will cost $9.99 USD.

And, as promised, all newsletter subscribers (that's you!) will get a coupon code that lets you buy the beta release for $4.99 USD! 

****************
Q1 2012 
Final release 
$9.99 USD 
****************

One last thing, if you guys could do us a big favor:

************************
Send us your SAVE FILES!
************************

Go back to the demo - either on our website (if you played the browser version) : http://www.defendersquest.com/play_demo.html

...or just run the executable version you downloaded, and press the "export" button on your game's save slot. This creates a ".dfq" file you can save to your hard drive. Take note of where the file is, and attach it to an email sent to this address:

lars.doucet+tdrpg@gmail.com

Please include "SAVE FILE" in the subject line :)

With all your save files from the wild, I'll be able to do more reliable testing to make sure that save games from the demo will import correctly into the final version of the game. Anyone who sends in a save file for testing will get a nod in the credits, so please supply whatever name you'd like to be thanked as in the email!

Thanks again for all your feeback, encouragement, and most of all PATIENCE, as we head down the final stretch!

Sincerely,

Lars Doucet
Level Up Labs

A Status Effect Stacking Algorithm

(Cross-posted on my Gamasutra blog, which usually gets more comments)

Status effects are a cool way to add strategic depth to both Tower Defense games and RPG's, and since  our upcoming title Defender's Quest is a hybrid of both, it's chock full of 'em, and unlike some RPG's, we took special care to make sure that they're not totally useless.

In Defender's Quest, each of your party members is a placeable "tower" in the battle system, but also a unique and persistent character who levels up and gains skills over the course of the entire game.  Some of these skills cause the defender's attacks to inflict status effects .

Here's a short list of fun things you can do to monsters:

• Poison - X damage / second for Y seconds.
• On Fire - X damage / second for Y seconds, cancelled by ice
• Chilled - creep slowed by X% for Y seconds, cancelled by fire
• Frozen - creep stopped for Y seconds, cancelled by fire
• Stun - creep stopped for Y seconds
• Bleed - creep takes X% extra damage for Y seconds
• Confuse - creep walks backwards for X seconds
• Blind - creep's attacks miss X% of the time for Y seconds
• ...and many more!
  

Ice Mage freezing and slowing creeps

The Problem

As you upgrade these skills, both the potency and the duration of the status effect goes up.  Shortly after implementing this system, I ran into a dilemma - what do I do when two status effects hit the same enemy?  This problem was particularly interesting because it was both a technical and a design problem.

Every status effect has two main variables - potency, and duration.  Potency takes on a different meaning depending on the effect - for example, in poison, "potency" means damage per second (dps); for slow, it represents a speed multiplier.  Duration, however, always means how many seconds the effect lasts for.  So, stacking status effects is all about combining potency and duration in a way that:

1. Is mathematically sound
2. Doesn't look like a glitch
3. Doesn't seem "unfair" 
4. Doesn't lead to weird edge-case exploits

There's several unique cases to consider, and ideally, one algorithm should be able to cover all of them.  Let's go through the cases one by one as I step through my problem-solving methodology and come to a final decision.  

1. Different effect types

This is the easiest case. First, check to see if the new status effect "interacts" with whatever is already applied to the enemy. If there's no interaction, then just apply the second effect - ie, an enemy can be bleeding and poisoned at the same time.  However, if the enemy was on fire, and we just hit them with a chill (slow) spell, then we need to remove the fire first, since one of our rules is that fire/ice spells cancel each other.  If we hit them with a freeze (stop) spell however, we'd cancel the fire, reduce the freeze to chill, and then apply that.  

2. Same effect, identical stats

Let's say an archer with poisoned arrows hits an enemy, and then hits them again, inflicting the same status effect twice at different times.  Let's say the first poison effect (A) is 10 dps for 5 seconds, or (10dps | 5s) for short.  This will deal 50 damage over the life of the effect. One second later, the archer hits the same enemy with an identical poison effect (B), also (10dps | 5s).  In this case, the variables will be the same, so it's pretty easy to combine them, right?

Not quite - the enemy has already been walking for 1 second before the second poisoned shot landed, so (A) is now actually (10dps | 4s).  Even with identical starting stats, duration for any two effects will almost always be different in practice.

In a world where we can expect potencies to remain constant, the natural choice is to add durations together.  Not only is this simple and intuitive to the player, the alternative method of making potency increase while keeping duration constant could make dps effects like poison really difficult to balance.

So, in our above example, we just add another 5 seconds to the poison clock and now our creep is poisoned to the tune of (10dps | 9s).  All is well with the world!

3. Same effect, different stats

This is where it starts getting complicated.  What if two different archers with different poison stats hit the same enemy?  The prior example was easy because potencies matched, but here both numbers are different so simple addition is out the window.

A naive way to "combine" the values is just to average the two effects, but this fails to "conserve" the full power of both. Individually, the first effect will deal 40 damage total, and the second 50, for a total of 90.  Averaging both effects to a single (15 dps | 3.5s) will only yield 52.5 damage, not what we want at all!

So, whatever we do, combining the two needs to result in 90 total damage at the end of the day.  More generally, the PotencyDuration value of the combined effect must equal the sum of the PotencyDuration of each effect taken individually.  This principle, "conservation of PotencyDuration," should work in all cases, no matter what values the status effects have.


Conservation of PotencyDuration

Mathematically, the principle can be stated like this:

PDA + PDB = PDC

where (P: potency, D: duration, A, B: original effects, C: combined effect)

So, the first thing to do is redefine Poison A and Poison B in terms of PD values:

Now, we just have to convert the PD of Poison C back into potency and duration.  There's several approaches we can take here - do we want to match the highest duration of the two effects, or the highest potency, or something else entirely?  All it takes to satisfy equivalence is two values that multiply to make 90, but each approach will have unique subtle effects on gameplay and feedback that we need to consider as well.

1.  Match Highest Duration

We matched the duration of Poison B, the longest-lasting effect, and converted Poison A's PD of 40 into an extra 8 dps. This dilutes Poison A's potency by stretching it out over a longer time.  We're good, right?

Well, maybe not. 

Take a look at this -
here's what the player sees: 

Archer hits a creep

Creep takes 20 damage per second

Second archer hits the same creep

Creep takes 18 damage every second

What????  In the player's eyes, the additional poison shot now causes the creep to take less damage. Sure, everything is still mathematically hunky-dory, and the player isn't really being screwed over - the same total damage will be inflicted, just over a longer time.

However, I'm not sure any of that will be clear - I can easily see players refusing to let two archers have overlapping targets, thinking this is "better" strategically since they've noticed that mixing rangers results in "lower" poison damage.

This is even worse if we were dealing with a slow effect instead of a poison effect.  In this case, mage A casts slow (50% | 2s) on a creep, and then mage B hits the same creep with slow (30% | 10s).

What the player sees is: 

1. One mage slows the enemy down
2. Another mage hits it with a second slow spell
3. The enemy speeds up!

In both cases Potency-Duration is conserved, but the player will be misled because their chief visual feedback is the size of the purple numbers bouncing off of the enemy, or how fast the creep is moving.

2. Match Highest Potency

In this case, we've made the combined effect match the potency of Poison A, the strongest effect, and converted Poison B's PD value into 20 dps for 4.5 seconds.  Instead of diluting Poison A, we're concentrating Poison B, squeezing it into a shorter time-frame so that the potency can match.  With this approach, the player will see no change in the amount of damage happening each turn, but the effect will last for longer thanks to the extra poisoned arrow.  The player will see the same amount of damage bouncing off the poisoned enemy every second, but each extra poisoned hit will keep the effect going a little bit longer.


Final Considerations
Before we conclude things, let's compare our solution to our original goals.

Is it mathematically sound?

Yep! We're conserving Potency-Duration, so everything's good here.

Does it look like a glitch?

Nope! By matching the highest potency, the player won't see enemies speeding up when hit by a slow spell, or poisoned arrows "reducing" poison damage.  Now, if an enemy is hit by a stronger status effect, they will see the enemy either slowing down even more, or taking more poison damage, but this seems like a natural result.

Does it seem unfair?

Generally this approach seems fair. In fact - it might be a gift to the player.  By concentrating weaker effects to match the potency of stronger ones, the player gets more of their effect's strength up-front.  Although the overall damage (in the case of poison) is the same over the effect's life-time, getting it done faster is almost always better in a tower defense game, since killing even one tile earlier can mean the difference between a close call and letting the creep reach the exit.

However, this "gift" to the player varies a bit with the effect.  A bleeding enemy takes more damage when hit.  This effect is more useful the longer it lasts, because there are more opportunities to hit the enemy and score bonus damage.  So, whereas poison becomes more effective with our algorithm, bleed becomes slightly less.  Something like slow isn't really affected - regardless of whether the slow spell is concentrated or stretched out, the enemy will reach the exit at the same time.  Given that the algorithm has a mix of positive, negative, and neutral effects on the various status effects, it seems like a good general approach.  Negatively impacted effects like bleed might need a slight balancing buff to make up the difference.

Does it lead to weird edge-case exploits?

The only exploit I can think of is this: grouping lower-level defenders with a single high-level one, who "primes" the enemy with a high-potency effect, thus allowing all the subsequent defender's effects to match that potency and add time to it.

Honestly, that sounds like a perfectly legit strategy to me, and I don't see it unbalancing the game.
Compared to the alternatives, this approach still seems the best.


Final Thoughts

There's one final approach we briefly considered and dismissed which I want to touch on again - allowing the potency to rise when mixing effects.  I decided against this one for several reasons: first, there's no natural, obvious formula for how much to raise the potency by.  Second, raising potency shortens the lifespan of the effect, which makes for less interesting gameplay.  Third, it's much harder to predict what would happen in game if effects can rise in power just by stacking, so it seems ripe for exploitation / wrecking balance.

I hope you've enjoyed this little exercise.  I found it interesting because it's a good example of a problem where technical and design needs overlap, and I hope it's useful to somebody in their next game.

If you have any ideas of your own, or can think of a better algorithm than the one I laid out here, do share your thoughts in the comments!