There are three answers to the question, "What makes good hard games fun?" IMO. First of all, they are reliable, and second is they're giving the player some advantages and making the game "fair" and the last one is getting the consequences of mini decisions you made (of course, I'm not including things like challenges, etc.). And Ikaruga IS reliable. Your main concern is not some input delay or thinking about if you're hitting the boss or not; the gameplay is responsive (and juicy!). The game gives you advantages like the center of the player is a hitbox etc., and the PC version has a continue option, but this is still an arcade game, so it may frustrate you on some occasions. And, of course, the thing that makes this game great as it is: "color-changing" mechanic. It's so simple, yet it's so deep, and it does make you those mini decisions and get their consequences like, "yes you're immune to the blue projectiles but is it worth it to spend your limited boss time?". The ost is pretty good, the sounds are decent, game looks nice and the story is surprisingly fun to read!