Good game. The text when you are supposed to drop from the ledge, maybe should be changed from Spanish(?) to English.
For the first boss:
1. he kind of becomes impossible if you got 3 of 4 hits in and fall down.
because he will just nonstop rain green balls down but only in the center area (basically from the middle platform to right in front of him, zero balls in the left of the room or such) and there's no way to jump through that without taking damage. Which will definitely kill you with that one meekly heart you have.
2. you can cheese him by not just jumping between the middle and the right temporary platform over and over, but rather jump on the very edge of the platform the boss is standing on. and just spam attack. his balls dont reach there and he is defenseless.
But gotta make sure you aren't too close as I did this the first time, when the boss died and exploded, the explosion killed me too.
Second time I likely stood a tick further away and didn't take damage at the explosion :-)
Now made it to the boss under construction too. Using that door there just makes the door entering animation but then you just stand there frozen before the door, unable to move anymore. Likely intended as there ain't more to load, I guess.
Game sometime is a bit too straightforward, but that's likely cause each level itself ain't too big. But good game.