Grok3 is free (for now) but there are a couple other AI assistants that people say are comparable.
Ironically enough this is a question you should be asking AI.

Notice how grok3 doesn't even list itself.

Ask it why.

Many people on X say that Claude 3.7 Sonnet is the way to go but Grok3 is also amazing.

Some of the advice I'm seeing is to use "deepsearch" for Grok3 to come up with a plan... A GAME DESIGN DOCUMENT to create a flushed out plan for the game. And then once you have the GDD you use the "think" functionality to give the AI more time to use the GDD to create the game. This way the AI might spend something like 3-5 minutes coming up with everything rather than trying to crank it out in like 20 seconds.