Classic snake, pure and simple, do I really need to say how to play snake?
the aim is to eat the single dots by steering the snake towards them, but careful, bite your self and you lose. controls are below

up: w or 8
right: d or 6
down: s or 5
left: a or 4

Sorry, no arrow key support, there are reasons for this, mainly the arrow keys being used for page navigation

hint: to use the numbers on the num pad, you need to have num lock on