Just found an interesting Atari emulator online to play Atomchess 6502 right away.

From https://github.com/nanochess/Atomchess-6502/blob/master/toledo_atomchess_6502.asm select all the source code and press Ctrl+C, then open the emulator at http://8bitworkshop.com and click on left side, press Ctrl+A and then Ctrl+V and et voila! :)

Amazingly this nifty project assembles all the source code right away and does syntax coloring, then the emulator runs it in real time.