I( love this game; one of the old Thing-Thing classics that I go back and play every so often, even now in 2016. The fact that I am still playing this ten-year-old flash game is particularly impressive when you consider that my Steam library numbers somewhere in 120+ games.
A good one for the ages.
However, I have a problem with this game. See, I was playing Sentry Bomber survival, and I said to myself, "I'll play to 1,000 kills". Well, one thousand became two thousand, then three thousand, then four, then five, then help I can't stop playing.
Also, if you want to kill the Cashier, just get 999 on any short-barreled firearm, the Five-seveN will do, and get as close to him as you can while still being able to hit him. He'll fire ineffectually, spraying the wall behind you with rounds, while you peg him in the head until he goes down.