Steer with the arrow keys or WASD. On a touch screen use the on-screen D-pad or swipe on the board. The snake moves one cell at a time, and pressing the opposite direction to the one you are travelling in is ignored, so you cannot turn back into yourself.

Leaving one edge of the board brings the head back in from the opposite edge, so the board behaves like a loop rather than a box.

Each piece of food you eat adds one segment to the snake. The run ends when the head moves into a cell that the body already occupies.

You score one point for every piece of food eaten. Every 5 points moves you up a level, and each level makes the snake faster.

Level 1 steps every 160 milliseconds. Each level removes 12 milliseconds from that interval until it bottoms out at 55 milliseconds, which you reach at level 10, after 45 points. After that the speed stays the same and the challenge is purely about space.

Your best score is saved in your browser under the username you pick. If you sign in, personal bests can also sync to your account.

Early on, plan around the loop: a long snake can pass through an edge and re-enter on the other side, which makes the board feel larger than it is. Use that to take the shortest route to food even when it is on the far side.

Avoid winding into a tight spiral. A spiral looks efficient until the tail is far from where you need space, and then the only open cells are inside the coil.

The idea goes back to the 1970s arcade game Blockade, in which two players leave growing trails and try to force each other into a collision. Single-player Snake became a household name in 1997, when a version was installed on Nokia phones. For many people it was the first video game they ever played.

• Move in long, regular sweeps, such as left to right across a row and then back along the next, so the free space stays in one connected region.
• Keep your head close to your own tail once you are long. The tail moves out of the way as you advance, so following it is the safest path.
• When the snake covers a large part of the board, ignore food that would force you into a dead end and take the route that keeps the most open space reachable.
• Watch two moves ahead at high speed. At the fastest setting you have about a twentieth of a second per step, so decide the next turn before you reach it.

At low levels the danger is simply being slow to react. Once the speed stops increasing, the difficulty is entirely about planning: the longer you are, the less room you have and the more every turn matters. A theoretical perfect game can fill the whole board by following a fixed route that visits every cell exactly once, but doing that by hand under time pressure is very hard.