start button should work in the options as well, took me a sec to figure out i can only A out of it.
the controls are heavy and the collisions are very unforgiving. you need to just as much as brush against the objects by a hair for things to register, it gets punishing especially when the game expects you to squeeze into tight corridors behind the enemies you just bounced off from. this happens a few times on level 4 and is highlighted by the single tile of spikes at the beginning of that map.
level 3 also had a spot in which i had no idea how to progress other than damage boosting from an enemy, wasn't a fan of that.
it took me a moment to get used to the fact the double jump you can do with the grapple has to direct you forward and i still think it's weird how useless clinging to the wall right next to you is. i think making things less punishing and introducing more margins of error (smaller hitboxes, snapping to the ground tiles, etc) and options for the player (hanging on to walls? directional double jumps?) to lean on would go a long way to make this game more enjoyable and less frustrating to play, along with giving the level design a lot more tools and toys to challenge the players with. i don't know how much you want this game to be hardcore stuff for people who cut their teeth on the bang-your-head-against-the-wall-until-you-win breed of platformers, but i think it's worth a consideration at the least.
that said i appreciated the health recovery pickups that were placed at exactly the right places and the autosave. the graphics and audio were slick for what they are as well.