You need extra free ram to play this game lag-free this game is not suitable for low end devices. Green Force: Zombies Unkilled is Back Again by Trinity Games with Partnership of Raptor Interactive. This is an ad-supported free version of the game. HD Version: Tested Frame Rates. Nexus 5: 71fps. Galaxy S4: 58fps. HTC Desire 600: 55fps. Galaxy SIII: 55fps. Galaxy SII: 53fps.