Monster Spawn Rules (New)

All naturally spawned monsters (SpawnGroup.MONSTER) are blocked except for zombies and creepers (via SpawnRestrictionMixin).
Day 1: Zombies do not spawn at all (creepers spawn normally). Zombies start spawning from day 2.
Zombies do not catch fire in sunlight and can spawn both day and night (no light level check at all).
Naturally spawned zombies have ~90% chance to spawn in pairs (simulating "double") throughout the game, starting from day 2.

Day Mechanics (based on real-world time, does not reset when server restarts)

Day Effect 1 No zombies spawn 2-10 Normal, not mutated yet 11-20 Start mutating (glowing) 21-30 Run faster 31-40 Can break blocks (slowly) 41-50 Health increases (+10) 51-60 Can place blocks (climb to chase players on high ground) 61-70 Break blocks faster + can jump over 2-block high walls (Goal pushes Y by itself) 71-80 Run even faster 81-90 Damage +2 91-100 Peak difficulty (all above effects combined)

Every morning (the first tick of the day) there will be a message showing the date + stage description in the chat.

4-Color Moon System (New: Random every 8-10 days)

Calculated deterministically from the world seed by simulating the schedule so that each special moon is spaced randomly 8-10 days apart (not the old daily probability), which allows "tomorrow's moon" to always be calculated in advance without needing a separate save file.

Red: Monsters spawning that night get stronger (health/damage/speed)
Yellow: Monsters become weaker
Green: Players get the Luck effect
Blue: Players get Night Vision