A pretty fun game with an original idea. Though, as other's have mentioned, it does suffer from the issue of being able to spam the space bar to constantly shoot down missiles. Could perhaps implement a recharge period or a refilling ammo counter.
Further, the game feels like it ramps up in difficulty way too rapidly for it to be a solid learning curve as you quickly become overwhelmed even if you are spamming the space bar, causing it to be impossible after a few seconds of play.