Here's my top score, at nearly four minutes survived:
There are a couple of problems to an otherwise solid foundation.
The first is that the camera is too close, most of the time the enemies you need to worry about are off screen. This makes it very hard to dodge them when you don't know they exist and difficult to hit when you do know their general location.
The other is that the upgrades for the player run out quickly while the enemies continue to gain in strength infinitely. In fact, after upgrading to Fire +4 the player is effectively as powerful as they can be when it comes to fighting back. It soon becomes a situation where the only choice is to run around in circles while being chased by an ever growing blob of bugs. Having 10 extra skill points and nothing to put them into is a bit disheartening!