PROS:
I like the freedom of vertical look with the mouse, which gives you some room to make some interesting mechanics that revolve around it.
The weapon felt very responsive to shoot and there was good hit feedback when you managed to hit enemies and cause damage.
CRITIQUE:
I wish the spiders did more to take advantage of the vertical look mechanic. Even so much as a hopping spider that forced you to look further up or specific locations on the spiders' bodies that act as critical hit damage points would let that mechanic shine.
The spiders weren't much of a threat when I realized that I could just walk up to them and they wouldn't deplete my only resource. That may have just been a "cut for the sake of time" thing, but it detracts from the "attack" portion of "Space Attack" ;).
It'd be nice to have some sense of progress as I'm playing the game just to help drive me to play it more. Something like a "Survival Timer" so that I can try and last longer on my next run or a "Kill Count" to give myself some kind of scoring mechanic to shoot for would help get me invested as a player.
It feels like there's grid-based movement here, but the grid itself is very small if it exists so you might be toe-ing the line on that piece of the rules.