Exceed 2nd is a bullet hell shooter that lifts its main gameplay mechanic from Ikaruga. All bullets/enemies come in two colors, and you can switch your own color to absorb same colored bullets (which recharges your invulnerable laser) while being vulnerable to opposite colored bullets. You also do more damage to opposite colored enemies, though it's often riskier to do so.
Exceed 2nd is more of a traditional twitch/reflex game than the puzzle shooter Ikaruga though. You can still apply strategy to the stages and bullet patterns to get better at them, but it has a lot more flexibility and room for improvisation.
The game also has a lot of aggression. You're encouraged to get close to enemies to melee them, and use your laser as soon as it recharges to kill bosses faster. It gives a great sense of risk/reward to the boss fights, since you can choose whether to try and kill them as soon as possible, or save your laser to protect you later. Combine this with how you damage bosses faster by staying close with the opposite color, and you have a very aggressive, up-close-and-personal game.
The level designs and bullet patterns are really solid, though maybe not as intricate or perfect as a Cave shooter. But they are fast paced and have a lot of intense moments. Overall the game is really, really fun, and I'd recommend it to anyone who enjoys shmups. It's the best Exceed game imo, and probably one of the best shmups on Steam if not the best as of this writing.