A bitmap graphics program for Commodore 64.
KoalaPaint was The Other Really Big Graphics Program in the C64 scene; the other was ArtStudio II.
The main difference between ArtStudio and KoalaPaint was that KoalaPaint worked in the full color graphics mode, while ArtStudio worked in high resolution mode (in which each 8x8 pixel area can have only one foreground and background color).
KoalaPaint used two screens: The other had all tools and palette, and the other had the picture being worked on (there were two different picture pages to work on).
To switch between the screens, one needed to move the pointer outside of the screen, until it sounded a "beep, beep, beep..." sound, and push the joystick button. I can still hear this sound echoing in my ears. It was a sweet sound.
KoalaPaint had only one BIG problem, IMHO: The file names of saved pictures. It used "xPIC A yyyyyyyyy" as the file name; the "x" was an unprintable character, yyyyy... was the actual name that you could enter, and it had sequential character identifiers for the files.