Mario first person game, help?

Hello I am making a Super Mario Bros. 3d in First Person. And I need help on making the enemies, when I touch them I lose a life, and if hit them on the head they die. Here's the video to show you the game, the progress of the game: [http://www.youtube.com/watch?v=AeSCAFziXew&list=UUw_DfacTczBOQh0RzFg-TXw&index=1][1] [1]: http://www.youtube.com/watch?v=AeSCAFziXew&list=UUw_DfacTczBOQh0RzFg-TXw&index=1