The game provides many interesting levels and challenges for each of them, but the final stage is incredibly frustrating. Half of the time the ammo is either being blocked by bullets or the bullets block both sides of the rails. If there was a more interesting mechanic introduced instead of just increasing the bullet intensity and making it nearly impossible to avoid the bullets at all. An indicator for the squares would also be nice, since it's difficult to tell how many bullets are needed to complete a square other than estimating off of the liquid inside.