Aftter discovering the game code is in GDScript, decompile it, and then recompile with edits. Modifying the `player_controller.gd` script, you can give yourself speed, jump, and fly hacks. Fly up to the big skull eye and get the flag. Make sure `FLAG_EYES` is in your `player.markers`.
Full writeup: [https://mahaloz.re/tasteless-21-tasteless-shores/](https://mahaloz.re/tasteless-21-tasteless-shores/)