Fun little jump&shoot.
It's a bit barren compared to it's inspiration (Megaman X) with no robot masters powers and no findable upgrades in the stages - you just find currency for shop that lets you buy them, and since you never need an upgrade to reach another upgrade in a stage, there is little reason to replay the stages or plan optimal route.
Other than that it's alright, all stages are interesting, each has a few unique enemies and hazards that fit the theme of the stage, controls are solid and responsive, the hitbox is a bit hard to judge at first but you can get used to it.
Music is pretty great with various Touhou themes remixed to replicate Snes/Megaman X style which fits the game pretty well. Speaking of Touhou - the story will probably be rather hard to follow for those that are not into the franchise as characters or past events that influence the story are not explained, but it's not a big issue as it is relatively simple.
The game is rather short but the additional challenges extend that playtime quite a bit if you are going for them. Probably more than a half of my 15 hours playtime was spend doing two hardest challenges in the game and while they were incredibly frustrating game was still fun enough to make me stick to it and complete them so that should tell you something.
Overall - pretty good, hoping for a sequel.