Everything I had to say about the base-game in my other review stands here too: little bit R-Type, little bit Galaxian, and a whole lot of quick fun.

But everything that gives it the replay drive and addictive energy to suck up hours of your time is here in spades. This game is hard, and yet you don't feel turned off for it. Not to mention it's a delight to look at without being overwhelming. Definitely going to keep playing this one for a long time, and glad I pitched in for this.