This is an awesomely fun game, I love swinging like spiderman, its especially satisfying when you can loop around a block and launch off of it. If there were more levels, I would have kept on playing.
I wondered how it would felt if the character had a little more weight to it, and I did encounter a few technical issues, sometimes it looked like the grapple should connect but I just kept on moving away from it and the line got longer but never pulled in. Also, sometimes the character and grapple gun could get into a position that made it hard to aim at the block you are standing on, effectively getting stuck.
Altogether this is an awesome piece of work and I hope you continue to expand on it.