I built a local fishing game with Claude Opus 5.5 and Unity 6 and the whole thing comes down to one rule.

Never ask for "A fishing game".
Ask for one piece at a time.

What came out: a beach, a pier, a day/night cycle, fishing controls that feel like fishing.

The order:

Step 1 -> Unity 6 project on the URP template, Unity's plugin installed in Claude Code.

Step 2 -> Greybox the level: simple shapes and a camera, zero art.

Step 3 -> The core mechanic in a single prompt, then play it until it feels right.

Step 4 -> Models from Tripo, cleaned by Opus in Blender, imported as FBX.

Step 5 -> Light, water, effects and sound at the very end.

Step 6 -> Opus runs an autopilot playtest and writes the bug list before touching any of them.

The split:

Unity 6: the world, physics, UI.
Tripo + Blender: every model.
Opus 5.5: scripts, scene setup, cleanup, tests.
Me: play it and decide what stays.

Commit after every step that works.
A bad prompt then costs seconds instead of an evening.