Tower defense games remain popular on phones. For the uninitiated, the basic idea of these games is that you erect gun towers that defend territory against enemy invaders coming at you along a maze or path. All the action can be contained within the space of a small screen. There's some interaction with the app, but there's also a "watch what happens" period. Tower defense games are easy to pause and pick up where you left off. Overall, a great fit for playing while you're out and about. Grave Defense Silver is one of the newer versions of the tower defense form that adds a back-story and some interesting twists.
The story? A global nuclear war drove all survivors underground to escape the radiation (timely, huh?). Those who remained on the surface turned into horrible undead monsters that hunt for living things to eat (zombies — this game is like a pop culture tutorial). The game begins as the survivors start to explore the surface again and must protect their enclaves against the monsters.
The twists? Monsters can travel on land or air. So, you must strategize over whether to place ground cannons or guns that can shoot into the air, otherwise the air monsters will fly past all your defenses. Also, in the middle of a battle, the monsters can shift to a new path of attack. Therefore, you must think on your feet, and adjust the position of your towers in mid-fight.
You accumulate money from every monster you kill, but in some cases coins will appear for a few seconds. If you tap a coin while visible, you'll score even more cash, which you can use to purchase more towers.
This 'Silver' version of the game features several battle scenarios, all for free. If you upgrade to the Gold version, you get even more. If you get stuck, or just want to ask a question, the game allows you to send an email to the developers, right from the app.