I played this game for a long time and made it pretty far through the levels without spending any money. At about 3/4 of the way through, it becomes kind of a grind though because the weapon upgrades get soooo expensive. I finally made a $2 purchase to support the developers because Id had a lot if fun playing the game. But, at the stage I was at, it didnt get me squat. Wouldve had to make another purchase to get a single next-level gun I needed. Bottom line, this game is great, and totally worth the download. You can play a lot of the game for free. BUT, you probably wont make it aaall the way to the end unless you drop about $10 or have waaaay too much time on your hands.