Can I clone a game's mechanics with an AI coding assistant? What's copyrightable in a game?

What should I check, step by step?

1. Write the mechanic as a spec in your own words (what the player does, how scoring, winning and losing work, the numbers you'll tune) and give the assistant that, not the original game.

2. Don't paste or attach the original's source code, decompiled files, ripped sprites, sound or music, or screenshots for it to reproduce. Decompiling can also break the game's license terms.
3. Make your own art, characters, UI, sound and music, or use assets whose license allows your use (commercial, redistributed in a build), and record each asset's license.
4. Change the presentation choices the rules don't require: board size, piece shapes and colors, layout, animations, end-of-game effects. The Tetris court pointed out the clone could have used a 15-by-8 field instead of copying 20 by 10.
5. Pick your own name, logo and icon. A title isn't protected by copyright, but names and logos can be trademarks. Search the USPTO trademark database (and the stores you'll sell in) before you commit.
6. For a commercial release, check patents on distinctive mechanics. Nintendo and The Pokémon Company sued Pocketpair in the Tokyo District Court in September 2024, alleging that Palworld infringes multiple patents. Patents are national, so check each market you sell in.
7. Check that the code the assistant writes isn't someone else's. GitHub Copilot can block suggestions that match public code on GitHub, and you should license-scan any libraries it added.
8. Read the store rules, which can be stricter than copyright. Apple's App Review Guideline 4.1 says not to copy a popular app or make minor changes to another app's name or UI, and not to use another developer's icon, brand or product name in your app's icon or name without approval.

What copyright covers in a game

17 U.S.C. 102(b): copyright never extends to 'any idea, procedure, process, system, method of operation, concept, principle, or discovery', however it is described or embodied.

• The Copyright Office's Games page says the idea for a game isn't protected, nor is its name or title or the methods for playing it. Parts of a game with enough literary or pictorial expression can be registered, such as the text of the rules or the art on the board or box.
• For video games, the code is protected by copyright, and courts have treated the audiovisual display (characters, shapes, colors, sequences and sounds) as protected expression.

The Tetris case: same rules, copied look

Xio's Mino didn't copy Tetris's source code, but it copied nearly all of the visual look. On May 30, 2012 the court granted Tetris Holding summary judgment on copyright infringement and on trade dress.

• The court agreed that the rules and mechanics of Tetris aren't protected, but held that their expression is. It listed the style and movement of the pieces, the 20-by-10 playing field, garbage lines, ghost pieces, the next-piece preview, pieces changing color when they lock, and the board filling with blocks at game over.
• It said these elements might not be enough one by one; it was 'the wholesale copying of the Tetris look' that decided the case. Xio was free to express the same rules in its own way.

Where an AI assistant changes things

Asking for 'an exact copy of X' or giving the assistant screenshots, assets or code to match pushes it toward copying expression. Asking for a mechanic described in neutral terms doesn't.

• Assistants can reproduce code they've seen. Matching-code filters and license scans catch some of it; reviewing what you ship catches more.
• A blanket 'no clones' rule in a team's or tool's policy is easier to apply than judging each request, and safer for a business, but it's a policy choice. Under US copyright the line sits at expression, not at the word 'clone'.