I'd suggest adding some screenshots on the game's page to make it more interesting.

Well the game is pretty fun but a bit hard :

• Dying from falling could be interesting, but dying after a 2 meters fall is a bit punitive.
• I understand the die&retry mood but the end screen is reaaaally slow, an instant Replay button would have be perfect.
• Being one-shot by robots is okay, but through a wall or a stair, it's unfair :p
• I like the weapon but the levels are way too ugly :l
• Jumping is  a bit difficult cause the terrain is slippery, so the platforms are terrible to play with. The character should stop instantly when the player stop moving, this kind of physics doesn't really fit the platformer levels.
• These physical bullets are fun to shoot, having to calculate their curves and stuff.
• Having to destroy robots to regain life is cool, you have to shoot, dodge and be agressive, I liked that mood.

I'm amazed that you managed to achieve all that in 12 hours!

Wow if this is really your first game this is great, my first game didn’t play close to that! So first to the things I would suggest that I would try to improve in an update or the next game:

More clean Graphics would improve your game or at list make the textures Higher Resolution 

The player Interface doesn’t seems to scale with the resolution but I would wait also for the other feedback maybe its only on my pc.

The learning Curve is a bit to hard I think maybe make the start level with a bit more health and one or two ammo more.

Some of your assets seems to fly in the first level.

The Controls fell great 

The Sound effects are good

Love the overall game concept with the Jetpacks

Sorry if this Feedback is sounding wherry negative but, remember its complaining on a high level I think for your first game and a deadline of 12h you made a great job!