Pros:
+ Pleasant music.
+ Solid controls.
+ Good enemy variety (they gain new attacks over time).
+ Equipment variety allows for a few ways to play later on. None of the weapons feel outright bad at any time, and some shine better against some enemies versus others.
+ Cute story; a small amount of story, but cute all the same.
+ Decent difficulty past early game. The difficulty will rollercoaster a bit as you gain new upgrades, and face new foes. There is a final stage dungeon that will challenge basically anyone.

Cons:
- Early game is extremely boring. You have to grind for a few hours in maps that you have no chance of losing in with piddly weapons, and no speed boosts. By mid game you gain better weapons, a speed boost, and at times somewhat of an actual challenge.
- Expect grinding. Similar to the previous point, there is a lot of grinding in this game. I don't personally consider this a negative, barring the early game, but anyone considering this should be aware you'll have to get a significant amount of materials to progress in the game.
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TL;DR: Solid game, I enjoyed it quite a bit.