Level 8-3 Achievement in Bullet Beat
Level 8-3 Complete
How to unlock Level 8-3All ten levels of the campaign can be played consecutively, although you strangely get kicked back to the main menu after every level. As noted in the roadmap, difficulty has no impact on achievements, so feel free to play on Casual. You will have a massive health bar (displayed barely visibily across the entire bottom edge of the screen) and you barely take any damage from enemies. Each level consists of shooting your way through various enemies until you reach a boss fight at the end. Enemies will randomly drop powerups, and these are key to making the levels very easy. Pick up all of the powerups you see, but the ones that make you shoot additional bullets or diagonal bullets will allow you to tear through the enemies and the boss.
The only other additional "strategies" to speak of are for the bosses at the end of the game. The boss in 8-1, for example, can easily be defeated by just sitting below him, between his two legs, and firing up at him nonstop until he's dead. The final boss, on 8-3, normally requires an annoying approach of waiting for the missile to be shot at you and sitting at the boss to make him shoot himself with his own missiles. This can be very tedious. A much faster method on Casual difficulty is to just sit right on top of the center part of him and shoot at it until he dies. You will take damage the entire time, but he will die before you run out of health. This shortens the boss fight considerably.
The following video, courtesy of Achievement Land, shows all levels in the campaign (not in their entirely, but briefly enough to show how they work). It also demonstrates both boss strategies I mentioned above. Refer to it if need be for any campaign levels, but the game is easy enough that you likely won't need to waste time watching a video before you play through it.