I've been playing through a few times, and now I feel like I can give a cohesive review on the game.
It's basically Touhou x Metal Slug, but on a loop; you scroll back and forth automatically shooting dispersing enemies, with occasional boss fights, and it seems like you just keep going until you collide with something. You have a one-hit-death, and sometimes it seems like one corner of Astro's arm cannon will hit something, and everything is over. It's not as bad as Flappy Bird, but it's a little close.
You blow up robots to collect the coins inside them, which you can use to upgrade your character's weaponry. There are occasionally boosts (which widen your range or make coins home in on you) or gems (which are worth more coins.) You can use emeralds to buy more characters, but so far, these seem to be only available by buying bundles with real-world money. The other characters include Ochanomizu, Tenma, Blue Knight, and Atlas (in his 1980s style.)
Astro's game over animation.
Soaring high in the sky, he may be 300 pounds but only in size...It's not a
bad game, but it's very clearly in its 1.0.0 stage. I wish I could unlock the characters instead of just paying for them. Maybe the emeralds become available by the eventual end of a level.