Demofruit is written in Arduino, so if you want to customize it go ahead and use the information on the next couple of pages to install Arduino IDE and set it up for use with the Fruit Jam.

Texture Conversion

The Rotozoom demo tiles and spins a 128×128 pixel source image stored in texture.h as an RGB565 array.

 Image requirements:

• 128×128 pixels (power-of-two - the demo wraps with a fast bitwise mask, TEXTURE_MASK 0x7F, instead of division)
• 24-bit uncompressed BMP (Windows/DIB), no alpha, no RLE
• Bold, high-contrast content — thick shapes, chunky patterns, or a strong central subject. Concentric shapes, mandalas, chunky pixel art, or a bold face/logo all work well.

Music

Each demo (and the menu) has its own soundtrack, played as a ProTracker MOD file. MODs are the native music format of the demoscene: a small bank of digitized instrument samples plus pattern data describing which sample plays at what pitch on each channel.

Playback uses pocketmod, an MIT-licensed MOD player, which renders the music in real time on core 0. The audio path is:

pocketmod mixes stereo float samples → converted to 16-bit → sent to the TLV320DAC3100 codec over I2S (via the RP2350's PIO + DMA).

Songs live in the sketch as C headers, one per slot:

Each header contains a MOD_DATA byte array; the sketch wraps each in its own namespace so they don't collide. pocketmod supports up to 32 channels, so 6-channel, 8-channel, and wider MODs play fine (not just 4-channel) — though authentic 4-channel MODs are the period-correct choice and mix with the least CPU. If a song fails to load, the sketch logs the failure and simply runs silent rather than crashing.

Converting your own MOD files

A helper script, mod2header.py, converts any ProTracker .mod file into the header format the sketch expects. It does a straight byte-to-array conversion — it does not alter the music.

python3 mod2header.py yoursong.mod song_4.h

The second argument is optional; if omitted it writes yoursong.h. To change a demo's music, convert your MOD directly to the matching song_N.h , then recompile. To change the menu music, target song_0.h.

Where to find MODs

• The Mod Archive  filter by license and by file size (leaner tracks make smaller headers and faster compiles)
• Compose your own in a tracker such as MilkyTracker runs natively on macOS, Windows, and Linux

 Notes on file size and editing

The bulk of a MOD's size is its sample data, not its pattern/song length. To shrink a header:

• In a tracker, the biggest lever is downsampling the largest samples in the Sample Editor (roughly halves their size per octave of rate reduction);  trimming silence and tightening loops also helps.
• Shortening the order list (how many patterns play in sequence) plus deleting the now-unused patterns/samples reduces size only modestly, but is the right tool for fitting a track's *length* to a demo.

pocketmod loops a MOD automatically at its end, so a clean loop point often matters more than absolute length. Whatever you edit, listen to the loop seam (play to the end and let it wrap) before converting to a header.