I recreated 3D Terraria using Claude Opus 5.5. 🤯

8 days. 346,000 lines of code. Zero lines written by me.

No Unity. No Godot. Just a custom 3D engine built in C# by Claude.

Here's what's already in the game:

→ 3,369 of Terraria's 6,029 items
→ 407 of 481 weapons
→ All 256 armor pieces
→ 313 of 327 enemies and bosses
→ Custom 3D models, animations, textures, sound effects, and music
The entire game is playable from start to finish. Most missing content is furniture, decorations, vanity items, and other details.
How did I do it?
Honestly, I just kept telling Claude to continue. I play the game, take screenshots, point out bugs or visual changes, and let Opus fix things and keep building.
It even created its own bot to playtest the game while I'm away.

Every asset is generated through code. No Unity, no Godot, no imported Terraria sprites, code, or audio.

I started on the $20/month plan before upgrading to a higher tier to speed things up, so this isn't what a week on the basic plan necessarily gets you.

And yes, it looks like Minecraft. 😭

This is just an unofficial fan project, made for fun. I've got almost 2,000 hours in Terraria, and I can't wait to play the finished version.

AI game development is getting WILD.