The formation comes from the day's map: enemies worth 10, 20 and 30 points and the yellow bosses, plus rows of shields that wear down. Bosses take two shots (turning orange after the first) and fire three times while diving. From wave 3 everything that dives shoots twice, and from wave 5 there can be two dives at the same time. The formation sinks a little on every sweep (and with every dive once four or fewer are left): if it reaches your height, the run is over. When you lose a ship, the next one blinks for a moment and nothing can touch it.