Four in a Row

Choose a column and your piece drops to the lowest empty space in it, exactly as it would on a physical board. Players alternate, and the first to make a line of four in any direction wins. If the board fills with no line, the game is a draw.

You can play with a mouse or a finger by choosing a column, or from the keyboard by tabbing to a column and pressing Enter. Each column tells a screen reader what it holds, whose turn it is, and which row the next piece will land in, so the board can be played without seeing it.

Zerdly uses the standard preset: a seven-column, six-row board, four in a line to win, and the player moves first. There are no house rules to toggle and no variant board sizes, so a result here means the same thing every time.

Undo is available in free play and in two-player, where it takes back the last move — against the computer it takes back both plies, since undoing one would simply hand you the same position with the roles swapped. Sound can be turned off at any time and the setting is remembered; nothing in the game is conveyed by sound alone. A game in progress is saved as you play and is waiting when you come back.

Versus the computer gives you six strengths. The weaker ones do not merely look less far ahead — they sometimes choose a move they can see is not the best, which is what makes them feel like an opponent rather than a machine with poor eyesight. The strongest never does.

Two players, one device takes the computer out of it entirely and you take turns on the same screen. These games are counted but not scored: both players are here, so there is nobody for Zerdly to call the winner.

Today’s position gives everybody the same four opening moves and the same opponent, chosen from the date in UTC and checked before it is offered — never already won, never winnable with a single tap, and never already lost. There is no undo, and the first result of the day is the one that counts.

Tactical puzzles are thirty-six positions across three tiers, from a win you can take right now to one you have to force three moves deep. Each has exactly one answer, proved by a solver before the puzzle is offered. A wrong guess costs you nothing and leaves the board alone.

The centre column is worth more than it looks: a piece there can belong to more winning lines than a piece on the edge, which is why strong play tends to start in the middle and work outwards.

Watch for a move that creates two threats at once. A single threat is blocked; two cannot both be, and most decided games turn on somebody building the second one a move before their opponent notices. The tactical puzzles are largely exercises in seeing that a move earlier than feels natural.

Count the row a piece will land in before you play. Filling a square below the one your opponent needs simply hands it to them, and this is the most common way a winning position is thrown away.

The whole game runs in your browser. The opponent thinks on your own device, and the puzzles are generated and checked there too, both in background threads so the page stays responsive while they work. No account is needed and nothing about your game is uploaded.

Your record, your saved game, your daily results, your puzzle progress and your sound and motion settings are stored in this browser only. Nothing here asks for a name or an email, and the Clear saved data button on this page removes all of it — and only this game’s share of it.

Is it really free, and do I need an account?

Yes, and no. There is no sign-up, no trial and nothing to buy. The game runs in your browser and never sends your moves anywhere.

Can I play against another person online?

No. Two-player here means two people at the same device, taking turns. There is no matchmaking and no online play, and nothing on this page pretends otherwise.

Does the computer cheat?

It cannot. The opponent works from the same move list you can see, through the same rules the board uses, and the difficulty setting only changes how far and how carefully it looks — never what it is allowed to know.

Why is the daily position the same for everybody?

It is generated from the date itself, in UTC, so every visitor gets the same four opening moves and the same opponent that day. It changes at midnight UTC.

Do the puzzles always have one answer?

Yes, and that is checked rather than assumed. Every position is put through a solver that finds every winning move, and any position with more than one is discarded before it is offered.

Where is my progress kept?

In this browser, and nowhere else. Clearing your browser data, or using the Clear saved data button on this page, removes it permanently.

• ChessSix levels, from a gentle start to a real fight.
• CheckersDraughts against the computer or a friend.
• NonogramPicture logic puzzles with a single solution.