Hei Eunege, I tested the game right now, It is very good!

I liked the fun story, the graphics are good, music and sound effects nice, playability is fun too.

The performance is good, It runs ok in an old 9 year desktop.

I missed a score counter (Am I too old school?)

I played it at medium dificulty, and even for my standards (I finished a dozen megamans decades ago) is hard.

For the nowadays game design patterns, it would be good to have finishable stages with a limited number of enemies, that would slowly becoming harder in the next stages. Finishable stages provide a reward for the player.

Excellent work, keep it up.