VERY repetitive, but fun for a while. The issue I had was when you get your speed up and go against harder enemies the bounce back pushes the hero off screen and since thats where enemies respawn, you can get the hero stuck in a spot that he can only die to get out of. And forget about trying to regulate speed past upgrade 40 because the hero speed, cursor position and camera speed get so out of whack that a single mouse click will send the hero passed the courser and therefor turn him around or shoot the camera way out in front so you loose where he is anyway...
That and the loading times (and this eats up shockwave on my system- crashed it three times before I realized that I had to close everything else just to get passed the LS at the end of Lvl 1) cost you points but it is still a good little time waster