Technocide

I played this game single player here and there. I'm not hardcore about bullet hell games, but I can hold my own and this game gave me quite a run for my money at normal difficulty (I'd say between 24-48 hours total and one successful run through is perhaps 1 hour). Even though each game is short, if you have a concentrated amount of time you can dedicate to the game (ie, maybe a day or two with nothing else to do), I recommend you do that. The game has some roguelite capabilities in that games are short and you get to keep one of the special systems you acquired for your next playthrough (for the first third of the game, they are not that great, but later on, they are powerful and give quite a boost). The game has some interesting twists compared to your typical bullet hell. The main goal of the game is not to avoid damage (although you want to, as it will disable you for a precious second or two), but to prevent enemies from reaching your mothership that is beyond the bottom of the screen. Each enemy that does do a point of damage and your mothership has 7 hit points at most. Damage to the mothership carries between missions. You get to chose between 2-3 locations on each mission with varying amount of difficulties and varying rewards. Some will repair the mothership, some will give you extra credits (which you can use to buy special systems), some will allow you to buy special systems at a store and some will give you a random special system. You also get 3 different main weapons (one you start with, the other two you acquire early on) that you can alternate and experiment with to dispatch different combos of enemies. The kinds of enemies you encounter evolve over the course of the game (well, none go away, but they add extra ones to the roster) and they are rather unique and interesting to tackle. You have two bosses and even with my OP specials, the end boss was a close call (though I beat him on the first try). The end game is funny and cute.