Choose Easy, Medium or Hard. Each round shows a random set of tiles for a short window, then hides them. You then tap the cells you remember until you have found all of them.

Only the positions matter, not the order you tap them in. Tapping a tile that was not in the pattern costs a life immediately. Running out of recall time also costs a life.

You have three lives per run. When the third is gone, the run ends. Getting a pattern right moves you straight on to a new one.

The settings for each level are: Easy is a 3×3 grid with 3 tiles, a 2 second look and 8 seconds to recall. Medium is 4×4 with 5 tiles, 1.5 seconds and 6 seconds. Hard is 5×5 with 7 tiles, 1 second and 4 seconds.

Every correctly recreated pattern adds a fixed number of points: 100 on Easy, 200 on Medium and 350 on Hard. There is no streak multiplier, so the score is simply the number of patterns completed times the level value.

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.

Do not try to remember individual tiles. Look for shapes: a diagonal, an L, two adjacent pairs, a corner and an edge. Three groups are far easier to hold than seven points.

Use the position on the grid as a code. Naming rows and columns, for example top row, middle column, can help you replay the pattern in words.

Gridlock relies on visuospatial working memory, the short-term store you use to hold a layout in mind for a few seconds. Classic psychology research suggested people can hold roughly seven items at once, and later work argued the figure is closer to four meaningful chunks. That is why grouping tiles into shapes helps: it turns many items into a few chunks.

This is a game, not a clinical test or a training programme. It is a fun way to practise paying attention, but we make no claim that it improves memory in daily life.

• Easy gives you 2 seconds to see only 3 tiles, so use the time to notice relative position rather than rushing.
• On Medium, look for symmetry. Five tiles on a 4×4 grid often form a recognisable shape.
• On Hard, you only have 1 second for 7 tiles on a 5×5 grid. Start by locking in the first cluster your eye lands on and fill the rest around it.
• After a wrong tap, take a breath. A new pattern begins immediately, and a rushed answer costs another life.

Start on Easy until you can clear ten patterns in a row without losing a life, then move up one level. The jump from Easy to Medium adds a whole new row and column and two more tiles, so expect your first Medium runs to end early. That is normal, and the second or third attempt is usually much better as your eye learns where to look.

Short sessions work best. Attention is the limiting factor in this game, and after a few minutes of play mistakes tend to come from tiredness rather than from a lack of skill. Stop when you notice yourself tapping before you have really seen the pattern.

Most of the pressure comes from the recall timer on each round, not from a global countdown. That means you can play a long run at your own pace as long as you keep getting patterns right. Three lives is enough to forgive a couple of slips but not a pattern of rushing.