Defines the terrain shape for each of 48 game levels. Each level contains 64 terrain fragments × 4 bytes. Loaded by render_terrain_row as terrain scrolls.

Byte	Contents
0	Profile (0-14): data_terrain_profiles index. 1=pre-bridge, 2=bridge, 3=post-bridge
1-2	Row offset (16-bit): shifts bank position
3	Bits 0-1: edge mode. Bits 2-7: island index (÷4 for data_islands)

When profile is 2 (bridge), the bridge destroyed flag is cleared. When profile is 3 (post-bridge), bridge countdown begins. Fragments wrap at 64, advancing to the next level.