Man this game doesn't F around! As soon as you have the grapple ability, the levels are instantly hard XD
Some feedback: I got quite a long way without learning you could jump just after grappling. I kind of cheaped my way out of the pit after getting the grapple. It didn't feel right but I didn't know what else to do.
The way I actually found out was when I got sick of using the keyboard and re-loaded the browser so it would detect my gamepad, and then accidentally triggered it; at first I thought he/she was climbing up off the corner of a ledge. After a few times I worked out what was going on.
Maybe it needs a screen right at the start where there's no walls or anything to jump off, just a platform that's too far to make in a jump, but you need to grapple off the side of it, then jump.