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Size optimization backlog

Flash budget is 16 KB. Read the real usage with:

riscv-none-elf-size tama.elf     # flash = text+data, RAM = data+bss

(Ignore .elf/.hex file sizes — they include debug info / ASCII framing and are not the flashed image. tama.bin is the true image.)

Current state (after the printf removal below): ~11.9 KB / 16 KB (~73%).

DONE

✅ Drop printf/snprintf — saved ~1.4 KB

Replaced every snprintf with tiny s_cat/u_cat string builders (in tama.c), disabled both printf backends in funconfig.h (FUNCONF_USE_DEBUGPRINTF/FUNCONF_USE_UARTPRINTF = 0), and stubbed the SSD1306 I2C driver's lone printf with #define printf(...) ((void)0) before its include. Result: mini_vpprintf + mini_itoa + mini_pad + _write fully garbage-collected. Readability: neutral/positive. No behaviour change (the stubbed printf only logged an I2C timeout we can't recover from anyway).

TODO — ranked by value vs. effort

1. Crop sprite frames — ~0.5–0.7 KB · low risk

Every creature frame is stored as 32×32 = 128 bytes, but the art only fills roughly the middle ~28 rows; the top/bottom rows are empty padding. ssd1306_drawImage already takes explicit width/height, so we can store shorter frames.

How: in sprites_gen.py, crop each frame to e.g. 32×28 (width must stay a multiple of 8; height is free). Emit the real height and adjust the draw y.
Savings: ~4 rows × 4 bytes × ~18 frames ≈ 0.3–0.7 KB.
Readability: art stays editable as ASCII; only the generator changes.

2. Alias more Panko frames — ~0.13–0.26 KB · trivial

Shell/Tmux already reuse 4 frames across the 7 expression slots. Panko (the panda) still has 7 distinct frames. EXP_BLINK and EXP_EAT could alias idle/happy with little visible loss.

How: in the species_frames[SP_PANKO] row of sprites_gen.py, point the blink/eat slots at pana_idle/pana_happy and delete the now-unused frames.
Savings: 128 B per dropped frame (1–2 frames).
Readability: neutral. (Trade-off: loses the dedicated blink/eat animation.)

3. Table-drive the beep jingles — ~0.1–0.2 KB · low risk

Many multi-call beep(...) beep(...) beep(...) sequences inline a lot of immediates.

How: store jingles as small {freq,ms} arrays and add a play(jingle, n) helper; replace the inline sequences with one call each.
Savings: modest, scales with number of jingles (~8 today).
Readability: arguably improves it (named jingles).

4. Trim the font table — up to ~1.5 KB · NOT recommended

fontdata in ssd1306.h is a full 256-char × 8-byte table = 2048 B; we only use ASCII ~0x20–0x7A.

Why not: requires editing the vendored ch32v003fun/extralibs/ssd1306.h, which is fragile across library updates and hurts ease-of-use. Only worth it if we're truly out of space. If done, keep a local patched copy and document it.

5. RLE-compress sprites — ~1 KB · NOT recommended

Sprites are mostly runs of 0x00/0xFF and would compress well, but this needs a decoder in the draw path and makes the art opaque (no more ASCII editing). Net readability loss; only revisit under severe pressure.

Already optimal — don't bother

Compiler flags: already -Os -flto -ffunction-sections -fdata-sections -Wl,--gc-sections. GCC has no -Oz.
RAM: ~55% used, not the constraint. The 1 KB ssd1306_buffer is mandatory (full framebuffer); don't touch.

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