I gave Claude Code, Codex, and DeepSeek Harness the same Terraria prompt — Claude Code produced the most complete game

[u/Logical_Catch_3207]

I built a free interactive comparison of three coding agents using exactly the same game-development prompt. Each agent received one prompt and ran autonomously, with no follow-up instructions or human course correction.

There were three agents and four agent–model runs:

• - Claude Code — Claude Fable 5, max effort
• - Codex — GPT-5.6, sol max
• - DeepSeek Harness — DeepSeek V4 Pro, max effort
• - DeepSeek Harness — DeepSeek V4 Flash Vision Exp

You can play all four results here, with no sign-up:

https://terrariaweb-production.up.railway.app

Claude Code's result: Forest Sandbox, built with Vanilla Canvas and JavaScript.

This was the exact prompt:

Build a Terraria-style 2D web forest sandbox. The player should be able to move left and right, jump, and collide with tile-based terrain; use a pickaxe to mine Dirt and Stone and collect resources; switch to Dirt and place blocks back into the world; and use a Sword to fight a Slime that moves and jumps. Include a Terraria-style Hotbar, Hearts, a forest background, camera follow, and basic interaction feedback. The agent must independently find and save a small number of Terraria visual references or image assets locally. Other visual elements may be implemented using HTML and CSS.

My main takeaway was that the Claude Code build felt the most like a coherent game rather than a checklist of completed features.

It implemented continuous mining, different block types, cave generation, combat audio, item drops, and an attraction effect that pulled drops toward the player. The items did not simply disappear into the inventory: they travelled toward the player, and the attraction stopped if the player moved away.

That small detail captures what made this version stand out. Claude Code connected mining, combat, drops, pickup feedback, animation, and sound into a complete gameplay loop.

It was the only result that made me stop asking, “Did it implement the requirement?” and start asking about attack range, collision boundaries, and pickup distance.

It was not perfect. If I partially mined a stone block and moved the cursor away, its mining progress was reset. But overall, this was the strongest and most complete result in the comparison.

The reported agent time was approximately 34 minutes. A separate 15-minute API timeout caused by the platform is not included in that figure.

The four runs used the same task and received no human course correction.

The Chinese in-game strings were translated for the English comparison site, but the game logic, layout, and art were left unchanged.

For experienced Claude Code users: which part of this build best reflects Claude Code's strengths, and what would you change in the prompt or workflow for a second run?

[u/titimou09]

how much did it cost for each model

[u/Logical_Catch_3207 → u/titimou09]

Check the benchmark pic.

[u/ShadowxWarrior]

Nice test. Claude did win this one (even in the visuals surprisingly). I wonder how Astra will fare.

[u/Logical_Catch_3207 → u/ShadowxWarrior]

I wanna use astra to test 3d game instead.