After merging new-newnassets, the rat sprite assets are now horizontal
4-frame sprite sheets (e.g. BMP_MALE_UP.png is 80x40 instead of 20x40).
The drawing path for rats inside internal tunnel passages still called
draw_image() without source_rect, so the engine rendered all 4 frames
side by side as a single wide strip (the visual artifact shown in
/tmp/pi-clipboard-...png).
This brings the tunnel-internal rendering in line with the non-tunnel
path, which already used source_rect = (frame * w, 0, w, h).
Matteo Benedetto
1627f58103