When aiming with scoped weapons, most noticeably with the sniper rifle, one pixel of movement with the mouse causes a much greater pixel movement on the screen. This sometimes makes it impossible to get a headshot on an enemy at certain positions. Other than that, this is a very fun game.
4/5. It would have been 5/5 but there was the problem of trying to move the box left or right when it was close to the edge of the screen. You should be able to control the box with the left and right arrow keys.