One road. Ten towers a side. Bring their fortress down before their bosses grow too strong.
Valor is earned only by winning a battle: more on harder difficulties and in full battles. Perks are dear: even the cheapest takes at least five won battles.
A second path changes how a hero fights. Unlock it once, then pick it on the hero screen.
The autosave is written every two minutes. Your own saves are only replaced when you choose to.
Raising the walls…
The Last Defense needs a wider screen. Turn your device sideways, or play on a tablet or a computer.