Defines what objects spawn at each scroll position for all 48 game levels (bridges). Each level has 128 spawn slots (256 bytes, 2 bytes per slot). Read by spawn_objects_from_level_slot during scroll.

Byte	Contents
0 (D)	Object definition: bits 0-2 = type, bit 3 = rock flag
1 (E)	X position ($00 = empty slot, $01-$FF = spawn X coordinate)

When bit 3 (SLOT_BIT_ROCK) is set, bits 0-1 select rock variant (0-3). Otherwise bits 0-2 are OBJECT_* type. Level address = level_objects + (level_number × SIZE_LEVEL_SLOTS).