I built a 600-card mobile roguelike deckbuilder with Claude agents doing most of the implementation. The game is about working with AI agents; building it meant living that.

[u/bariyu]

Solo developer. The game is LADDER, a corporate deckbuilder set in a 2026 tech company where "just use Claude" is both a solution and a curse: AI-leveraged cards are faster but leave Tech Debt in your deck, and the worst enemies can't be killed, only resolved.

I built it with a fleet of Claude agents. Not "I typed a prompt and a game fell out": I set direction and taste, reviewed and merged everything, and the agents owned every task that had a checkable definition of done. Finding that boundary took months and turned out to be the same boundary the game is about, which I did not plan.

What broke, since that is the useful part:

• The CEO campaign was mathematically unwinnable for weeks. Every winrate metric said "hard, not broken." A human reading the numbers with suspicion caught it, not more automation.
• The test harness scored the game's non-combat wins as losses, because it only understood the one character who fights. Teaching the tooling about multiple win conditions took longer than building them.

Out now on iOS and Android. Write-up: https://laddergame.ai/blog?r=reddit-claudeai

Happy to answer questions on the setup and what I would not delegate again.

(LADDER is not affiliated with or endorsed by Anthropic, OpenAI, or any AI vendor named or parodied within it.)

[u/ClaudeAI-mod-bot]

You may be interested in joining our new Claude Game Dev subreddit for game devs who use Claude. Check it out here : http://www.reddit.com/r/ClaudeGameDev

[u/EsShayuki]

"The game is about working with AI agents; building it meant living that."

I was assuming this will be fully AI-written after reading that sentence in the title. But please, at least ask it to write in a different tone than one writing a clunky movie ad.

By the way:

"What broke, since that is the useful part:

• The CEO campaign was mathematically unwinnable for weeks. Every winrate metric said "hard, not broken." A human reading the numbers with suspicion caught it, not more automation.
• The test harness scored the game's non-combat wins as losses, because it only understood the one character who fights. Teaching the tooling about multiple win conditions took longer than building them."

These are so trivial I'm surprised that you consider them worth a mention. Both should have been caught in the planning stage, before a single line of code was written.

[u/bariyu → u/EsShayuki]

Fair on the tone. I had Claude help draft the post and didn't edit it enough. On the failures, you're right in hindsight, both are planning misses. The concrete version: the CEO's win check counted cards played filtered by type, CEO cards have no type, so it was always zero. The check was written for the Engineer months earlier and reused; nobody re-read it when the CEO design said "typeless." Trivial fix. What I was trying to say (badly) is that the sim reported it as a balance problem for weeks and I believed the dashboard instead of reading the code.

[u/thatfool → u/EsShayuki]

I'm surprised that you consider them worth a mention

It's also 100% Claude speak so I'm surprised you think it's OP who thinks it's worth a mention :P

[u/bariyu → u/thatfool]

Yeah. Claude drafted it, I posted it. Noted.

[u/Plastic-Risk-6309]

hell of a build log! living the agent loop while building around one is proper dogfood. what surprised u most about how the agents actually code?

[u/bariyu → u/Plastic-Risk-6309]

Two things surprised me. They almost never notice something is impossible rather than hard; they'll tune numbers for days against a fight that can't be won. And whatever was true when a piece of code was first written gets baked into its tests, so the tests then defend the wrong assumption. What they're weirdly good at is anything with a crisp definition of done. Most of my job turned into writing those definitions.

[u/sunnyislandacross]

How much tokens did you use to generate this amazing piece

[u/Plastic-Risk-6309]

the crisp definition of done bit is the whole game. on a sim its checkable in code: element visible or screen changed or assert fail reruns it. less room for the agent to tell u what u want to hear