fun game... a but repetitive, but an easy tip is to upgrade your regular arrows and buy all three elements, and upgrade to the point that you have a wall of arrows going, then hold "asdf" and click off screen. it will auto fire and then all you do is set and check back every minute er so.
i say its a mediocre game on any level, and the fact its free makes it worth playing. weapons are fun bosses reward you with large explosions and really it covers all of the basics. nothing above the bar but a well done game.