Something odd I noticed is that you have two textboxes for the score. It would look more profession if there was only one.
Another thing is that right clicking == godMode. True.
Time you spent alive should be converted to point of some kind and then spent on either moving to the next harder level or something to increase your likely hood of survival.
For the upgrade shop you could have; Extra lives in the game, Some rage meter thing that destroys some of the bullets, Ability to destroy a bullet in some fashion after some amount of hit, ability to slow the game down, ability to damage the central turret, place your own anti-turret.