Twelve fighters drop onto the island and only one can win. Look for yellow chests near the buildings: they hold shotguns, rifles, snipers, shields and health. The purple storm closes in over time and hurts anyone caught outside the safe circle, so keep moving toward the middle of it.
On a phone: drag with your left thumb to move. Touch the right side to shoot: it aims at the nearest enemy automatically, or drag with your right thumb to aim yourself.
On a computer: W A S D to move, aim with the mouse and hold the button to fire (or hold space to auto-aim).
The small map in the top corner shows the safe circle (purple) and everyone still alive. Fallen players drop a chest with loot.