I'm making a Super Mario Maker/Super Mario Kart fangame in Godot called Mario Kart: Track Maker! You'll be able to select from different environments from the original SNES game, and a few others. It'll have different grid layers where you'll be able to place track elements, and once you're done you'll be able to play it and export it as a special .mktm file to share with your friends! Unfortunately, it's still in development, so until it releases you can make suggestions here and check the below post for progress updates.

To-Do:

• Add all SMK characters
  
• Add track themes
  
• Make grid system
  
• Make all elements
  
• Make UI
  
• Release project
  

Hiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii!
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Oh yeah I forgot about this; no longer working on it anymore sorry