Rainbow

Rainbow is an IDE with built-in tools for graphics and sound using a dialect of BASIC to allow easy creation of simple games and applications for the Sinclair Spectrum, C64 and Amstrad CPC.

(Early MSX/2 support added)

This allows (mostly) the same code to be compiled for all three platforms, including attempting to use the same assets.  However, there is also the ability to use conditional compilation to make changes for each platform and the ability to use different assets including graphics, music and character sets.

Rainbow is written in Flutter and is open-source

https://github.com/jonn-reenthused/Rainbow