Snake.io

The Slither format rather than the Nokia one. You cannot die by hitting a wall or by eating yourself — you die by touching another snake, and everyone else is trying to arrange exactly that. Cut across a rival’s head and their whole body becomes food.

There is a live scoreboard down the side, so you always know how far you are from the top and how much of the arena wants you gone. The opponents are bots, not other people: single-player, in a format that usually is not.