Bullet hell -
- is the usual term for this sort of game. Essentially you have to dodge an idiotic number of projectiles, which is actually easier with a mouse than with a control pad - but here you have a cripplingly slow main gun which takes forever to whittle away at a boss' health; luckily it fires on its own, there's no way you could pay attention to shooting while making the tiny adjustments to squeeze through the 9,000 projectiles on screen at any given time. There's literally only one strategy that works: upgrade your bombs, then fire them off one by one and hope they do enough damage to stop the boss, since your main gun is essentially worthless. Boring, repetitious and any sense of reward dropping a boss may give you is stolen by the simplistic strategy and the fact that it is nothing BUT bosses.