Managed to clear all levels, but without any of the collectibles, so there goes my 100% MLG pro run. At times the physics still seem a bit off. My go-to example would be level 3: When you're trying to build momentum to get through the hole, you never seem to be able to go beyond a certain point of speed.
As far as controls are concerned, I had a little trouble with shift and control, you know when you're moving with the WASD and your pinky finger has to manage both keys at the same time it can be a little slippery. Though I'm more of a controller guy anyway, so take my PC control advice with a shovel of salt.
I feel swinging mechanics always lend themselves to large levels, so I'd like to see some larger levels, maybe with checkpoints thrown in, so you can keep the difficulty as challenging as in this demo. I think the difficulty was what I really enjoyed, levels were challenging and it felt rewarding when you finally find out the approach to beat them (1 and 3 more than 2 and 4, 3 in particular required some pixel-perfect maneuvering). Then again, I'm not sure if you're going to keep working on Grapplr, it seems more like a side project anyway, right? I mean there's a distinct lack of moth girls flying and rolling around. Either way, fun demo, thanks for sharing!