Survivor.io, is a smartphone game that has been sweeping the gaming community. Despite its popularity, many people still haven't heard of it, even though it's totally free to download. On the other hand, its addictive nature means that users soon become hooked after downloading it.
Tell me about Survivor.io.

In the survival/action game survivor io, you take control of a character who must fend off hordes of undead. You'll begin with simple weaponry and a leisurely pace, which is really beneficial because there aren't many foes in the beginning. But be prepared for an onslaught of zombies, some of which will be larger and more powerful, as you progress through the levels. Fortunately, you'll be able to deal with them better with the weapons you earn as you progress.
Rules for Survivor.io

The simplicity of Survivor.io's gameplay is part of its charm: you control your character using a virtual joystick located at the bottom of the vertical screen. Because your character fights automatically, all you need to do is move about. When you beat the zombie hordes, an experience meter will fill up at the top of the screen. This will unlock and upgrade abilities automatically.