To kill the gray you should hit once so it turns to metal and then hit it again right away it won't have time to turn to metal again. To kill a void eater wait till it start's to make its ray then run pu and whack it.
The idea of this game is good but the mixture of the diffculty and the lives is pretty bad. The only way you can actually win is by playing it in ghost mode and then in the other modes and I don't think that many people are willing to play this game that much.
This is a great game.The plot is great and the music is really relaxing 5/5 also if you can stay on the ground and just catch coins from bombs if you want some easy money