Great job on the game! I got to the end but it took me a bit longer than 2 minutes (heh), got 3 of the guns, and 4 of the stickers. Thoughts so far:
+Kitty is cute, she reminds me of a grumpy cat
+I appreciate the very self aware dialog options, kitty's backstory seems quite tragic
-mouse and keyboard controls (as others have said) take a little getting used to, I think over-the-shoulder aim is fine but you might have it toggle-able instead of needing to hold down. A button that aims the crosshair straight down might be nice too for gun hops.
-The ladder puzzle gave me some trouble, I saw you could toggle buttons on and off, but there didn't seem to be a combination that reached the ground floor, so I ended up positioning the ladder before hand and then using my shells to jump from the hill to the diagonal staircase. (If I had the 4-shot shotgun by then I'd have just jumped on the ammo vender to get up, but I only had the 2-shot)