Took me reading the controls and some experimenting, to figure out that what I thought was a huge bullet, was actually my grappling hook (Explaining why it didn't hurt anyone). Maybe you should try to have it ejected from one of the sides, so it's rope-hookness is more obvious to the first time viewer.
Switching between the gun and the hook is unintuitive. Since using the hook is exclusive with the guns, it would be reasonable to assume that you would switch to it the same way as you would with the guns. That said, I am not sure if you should keep the guns and the hook exclusive to each other, and instead not let the player swing and gun and the same time. It is the name of the game after all.
You also need a health bar, because I do not know how close I am to dying, and even need a few seconds to figure out I am dead, as no end screen appears, I only lose control as the fade out is very slow.
You could also do some sort of view of the objective, so the player knows what they are looking for.
Enemies move too much into your face, obstructing your view is their main way of killing you, aside from swarming you.
Your level is nice though. Probably doesn't have the versatility to get through 30 of them without becoming stale, but it is a great start, and adding some color variation should be much easier than the work you've already put into it. Looking forward to more.