- Replace time-based splitAt/splitDone with screen-space Y zones (SPLIT_ZONE_1
at top third, SPLIT_ZONE_2 at halfway) for more predictable MIRV behavior
- Add MIRV_RESPLIT_WAVE (wave 8): from wave 8 onward, MIRV buses split twice
instead of once, creating more late-game pressure
- Lower early-game difficulty: MIRV starts at wave 3 (was 6), reduced base
chance (0.05 vs 0.15), increased growth rate, lowered max (0.4 vs 0.5)
- MIRV trunk continues flying toward its target after each split
- Updated verification tests for split-zone geometry and new missile fields
- Cleaned up obsolete splitAt/splitDone fields across test fixtures
Brian Fertig
6cef254dde