The grappling mechanic is cool as heck! I'd like to see it more developed.
Visually it's pretty amazing. Liked the art and it was especially cool that you guys managed to get an intro with images (although one of the last ones I didn't understand exactly what was depicted). The tutorial is pretty cool and the only minor problem I had with the graphics were the green/orange-ish spikes on the walls, they felt like they blended a bit too much with the background so I didn't figure it would kill me, until it did. Also, the jumping and spinning while double jumping are super charming, kudos on the animation.
On the sound department I think music is a must in this game. The frustration from dying time and again felt worsened by the sheer silence. I like the jumping sound effect but the dash one was quite uncanny, felt like Gigio was suffering somehow. The death sound is super cool though! And brutal.
I really enjoyed my time playing with the grappling hook, but Gigio's momentum is a tad too unforgiving. I actually gave up on the tutorial because I kept on falling while in the jumping parts. His falling speed felt a bit too fast, making missteps pretty certain death as it was near unreactable to me.
Also, regarding the checkpoints, I've reached a few of them but I'm not sure they are working because when I die I seem to return to the beginning of the map. Maybe some indicator of how deep you are could help?
Other than that, there were some really minor typos that you guys are probably aware, like the "Options (not aviable)".
All in all, I had a lot of fun trying to survive falling around. The grappling mechanic really is super neat and when you get to save your skin using it, avoiding spikes by an inch, it feels amazing! Congratulations guys!