David Schmenk has just released v1.0 of the developer preview of PLASMA.

Modern Retroprogramming on the Apple II. When was the last time you programmed a modern language on a 40 year old computer? Now is your chance. PLASMA is a combination of operating environment, virtual machine, and assembler/compiler matched closely to the 6502 architecture.

Check out the Release Notes for details: https://github.com/dschmenk/PLASMA/blob/master/doc/Preview%20Version%201.0.md