There are two season in game: Peace Season and Meteor Season. Meteor season begins when you discover the surface. Season counter increases at 0:00 in every cycle (not every 600s). Peace Season lasts 4 cycles, with no meteor. Meteor Season lasts 10 cycles, and can be divided into two parts: Break and Meteor Shower. Break lasts 300~1200 seconds, without meteor. Meteor Shower lasts 100~400 seconds. A new comet will drop every 1~1.5 seconds.
Three kinds of co