Hello; I used:
- SDCC: a C compiler for old 8-bit CPUs;
- devkitSMS: a SDCC-compatible library for making games for the Sega Master System;
- PSGLib: a SDCC-compatible library for playing music and sound effects on the Sega Master System;
- BMP2Tile: a tool to convert images to formats compatible with the Sega Master System;
- RgbQuant-SMS: to optimize images to reduce tile count;
- Gimp: for editing the images;
- Tiled: for editing the maps.