(I am now in a rush to test as many games as possible to help, so please do not mind the cursory reviewing style.)

Controls are QWERTY-only instead of layout-independent (I have an AZERTY keyboard). Makes my life hard here… ._.

I like the grappling hook!

Level 3: stuck! ._. No idea.

no button to go back to main menu?

Level 4: I got all keys and tried all green zones, but to no avail…

Level 5: aaaah, you can PUSH the boxes! :D This must be the solution to level 3; I thought the display was merely buggy, it is hard to see that you are pushing them!

Back to level 3: does work! :) Solved it.

Level 6: wow, I realize the grappling can make you like Spider-Man! :D Great!

Level 7: this labyrinth is almost a chance game! All rooms look almost the same; some differences would help.

Giving up!

Level 8: nasty trap. XD Actually, I started going after the three keys, but banged into the surface, and THEN saw the fourth. ;)

Level 9: solved

Boss: nice scenery! :) Wow, he is huge! I like how you animated him, including his eyebrows. :)

How does he hit the player?? I see I lose health. (Got it: raises yellow below; you have to grapple. Can also bring walls, and heal.)

By the way, was the gun useless before this fight? It looks like so.

BEAT HIM! I was lucky: he only used healing and walls.

I wished the ending screen was different from the game over screen! XD Also, no explanation for the story, in the end?

I think the concept (especially the grappling gun) is interesting! I am less convinced about the link to the constraint, because the levels get different. Some indications, especially sounds, would help understanding how the elements work (such as pushing a box, getting a door-opening key), but this is already rather understandable. I had a good time, beat all levels except 4 (did not understand, maybe I missed the correct exit?), 5 (out of laziness! XD), and 7 (too hard for the little time I have!).