itch.io

There's no hard-coded highest level, and I'm not aware of any kill screen though I never tested it at such level numbers so I can't say for sure.  If you've played that far I hope it means you're enjoying it!

The latest version of GB Studio includes the ability to translate the standard shades of green to Game Boy Color-compatible colors under the Settings menu.  Right now you're restricted to just four colors across the whole game (only three of which can be used for sprites), which is why this game uses only black, purple, pink, and yellow.  The developer of GB Studio is working on an full GBC color for a future update, though.

Finally figured out how to get that last star!  This is a great demo, and a good example of how GB Studio can be used to create something other than an RPG or adventure game.  Also, really nice of the custom palette feature in GB Studio.