Claude Code in Unity: We Benchmarked It on a Game

In a benchmark of AI coding agents building a Flappy Bird game in Unity, Claude Opus 5 scored 10/10 and shipped a working game with a 306-line PlayMode test suite, while Claude Sonnet 5 scored 5/10 because it placed the ground at y = −250, making the game unplayable. DeepSeek v4 Flash, a free model, delivered a full game for $0.61, and DeepSeek v4 Pro matched the 9/10 score but cost $11.96 due to zero cache reads. The benchmark, run by Ziva in the Unity editor beta, used three prompts with a 20-minute cap per model.

Claude Code in Unity: We Benchmarked It on a Game Ziva runs docked in the Unity editor now, in beta, so we reran our Godot benchmark /blogs/gpt-5-6-benchmark-godot there: build a playable Flappy Bird as an agent, three prompts, 20-minute cap each. Claude ran on a Pro/Max subscription . | Model | Tool calls | Wall time | Build cost | Rubric | Stars | |---|---|---|---|---|---| | DeepSeek v4 Flash free | 158 | 45.6 min 2 capped | $0.61 | 9/10 | 3/5 | | DeepSeek v4 Pro | 413 | 42.9 min 1 capped | $11.96 | 9/10 | 3/5 | Claude Sonnet 5 BYO | 384 | 28.2 min | $7.34 | 5/10 | 2/5 | Claude Opus 5 BYO | 213 | 33.6 min | $14.73 | 10/10 | 4/5 | List-price equivalents, not billed: Claude ran on a subscription and this account has a 100%-off promotion on Pro. Flash’s 61 cents is real spend. Sonnet 5 wrote the cleanest code and a game you cannot play. The scripts are correct; the scene is not. The camera sees y −5 to +5; Sonnet put the Ground at y = −250 , so the bird dies before the first pipe arrives. Opus 5 shipped a working game and, unprompted, a 306-line PlayMode suite — twelve tests, run sixteen times, ending at thirteen passing. One failure “an in-flight keypress must not skip the overlay” is why it added a restart delay. DeepSeek v4 Flash , the free model, shipped a full game for 61 cents — built entirely in code — but capped on two turns. Same prompts cost $0.18 in Godot . DeepSeek v4 Pro matched that 9/10 in 413 calls, but made zero cache reads to Flash’s 10.4 million — most of the twenty-fold cost gap. Unity went from 12 tools to 21 this release, adding run tests , find gameobjects and manage asset . Two of four models used run tests unasked. Caveats: n=1 per model, one task type, wall times not comparable across engines. One Unity-beta defect cost three runs — a changed-API edit raises a modal dialog that blocks the editor, and -accept-apiupdate doesn’t stop it. The beta is in Ziva /blogs/best-ai-tools-for-godot-2026 .