For some reason it was too laggy for me (Opera browser). Looks good though, could've been enjoyable I guess

The idea of toting both a gun and a grapple hook to get out of a hazardous robot lab sounds pretty nice. And I appreciate your level design, too. Last thing good I can say is that the spritework on the enemies looks great. Unfortunately, the game has some prevalent rough patches that I think have to be fixed:

-Moving either left or right in the air means that you have to be okay with moving either left or right in the air until the moment you touch the ground. This makes the platforming difficult in ways that it shouldn't be.
-If you are pressed up against a wall and shoot it, your bullets can go right through the wall and net you some cheap enemy kills.
-If the spider boss does contact damage to you, the contact damage sound will play for every frame that you're in contact with the spider boss instead of just once for each time you get hit.
-The game can get a little laggy right before the boss level.
-I only experienced this once, but I think some enemies can just kill you outright for touching them. It happened to me with the helicopter drone that hovers in place and then charges in the direction of the player when the player is in proximity of it or fires at it.

If you flattened these sharp edges, and maybe got rid of that Mega Man model, you could wind up with a better game.

The game is playable. But not good. The controls are horrendous. The jump is to floaty. The wall jump is pointless since its not used in interesting ways. The gun that you use shoots way too fast and the re colored mega man sprite you used when walking backwards just does a moonwalk. Again, playable but not good.