Sim6502 platform compiles programs that can be run in 6502 Simulator by Michal Kowalski. You can download it from here.
Use -P sim6502 switch to compile a program for 6502 Simulator platform.
atalan -P sim6502 hello_world
Generated binary programm has XEX extension. This is executable in Atari format, that can be loaded by simulator using File/Load Code command.
Output is printed to the simulator console using built-in memory mapped IO ports ($E000-$e006).