You are the master of a small plot of land with a lot of paths. These paths have recently become infested with beasts and monsters trying to walk on them. You only have so many lives before you can't take anymore monsters and give up. Build towers along your path with the mouse and strategically place them to best handle all the waves of beasts coming. Upgrade your current towers to make them strong to prepare for the harder waves of monsters. Research new things in order to obtain upgrades and to give yourself that edge you need to beat back every wave of monsters and win.