Neutron Strategy: Controlling the Shared Piece

Updated October 2026

Neutron is a small game with an unusual tension at its heart: one piece belongs to nobody, and both players take turns pushing it towards their own side. Every move you make with it is also a gift to the opponent, who moves it next. This guide explains the exact rules used on this site, how a round is won or lost, how the computer opponent grows stronger as your streak rises, and the thinking that keeps the shared piece working for you.

The board and how pieces move

The board is five squares by five. Your five dark pawns start along the bottom row, which is your home row. The computer's five light pawns start along the top row, which is its home. The neutron, the single shared piece, starts on the centre square.

All pieces move in the same way. Choose any of the eight directions, straight or diagonal, and the piece slides as far as it can until the next square is either off the board or occupied. It cannot stop partway, and it cannot jump. Nothing is ever captured; pieces only block each other.

Each turn has two parts in a fixed order. First you move the neutron, then you move one of your own pawns. The only exception is the first turn of a round: the side that starts skips the neutron and moves one pawn only. On this site you start the first round of a game, and the starting side then alternates every round.

The interface does most of the bookkeeping. When it is time to move the neutron, every square it can reach is highlighted, and a reachable square on your home row is marked as a winning move. After the neutron, tap one of your pawns to see where it can slide, tap a destination to finish. Tapping another of your pawns switches the selection, and tapping the same pawn again clears it.

How a round is won and lost

You win the round the moment the neutron lands on your home row. You also win if the computer begins its turn with a neutron that cannot move in any direction, or one whose every possible slide would end on your home row.

The same rules work against you. If the computer slides the neutron onto the top row, you lose. If your turn begins with the neutron completely blocked, or with every one of its slides ending on the top row, you also lose. The game never lets you choose a slide onto the computer's home row; those squares are simply not offered.

If you move the neutron and then find that none of your pawns can move at all, the turn passes without a pawn move. A round is declared a draw after 120 turns in total, counting both players, which is 60 each. A drawn round ends the game just as a loss does, so the streak you had reached is final and can be saved. In our test of 800 computer-against-computer rounds only one reached the limit, so draws are rare, but a cautious, shuffling game can get there.

The question to ask on every turn

Because the opponent moves the neutron next, the most important square is not where the neutron goes now, but where it can go from there. Before you confirm a neutron move, picture every slide available from its new square. If any of those slides reaches the top row, you are offering the computer a win, unless your pawn move that follows closes that line.

This is where the second half of your turn earns its value. A pawn move can be a block: a single pawn placed on the neutron's route to the top row stops it short. Since pieces slide all the way, a blocker does not need to be adjacent to the neutron; it only needs to stand somewhere on the line, so that the slide stops before reaching the far edge.

The reverse is your attacking idea. A neutron position that the computer cannot move safely is a win for you. If every slide it has leads either to your home row or nowhere, the round ends in your favour before it even moves. Crowding the neutron towards a corner or an edge, so that your pawns and the board edge cover its exits, is how most strong wins happen.

Pawns as walls, not runners

Your pawns never score by themselves. Their only job is to shape where the neutron can stop. Good positions keep them spread so that they cover several lines at once, typically one or two staying near the bottom to protect your own exits and the rest standing in the middle rows where they cut lines towards the top.

Avoid moving a pawn just because it can make a long slide. A pawn that rushes to the top edge often opens a lane through the middle of the board, and that lane is exactly where the neutron will travel. Before each pawn move, check which lines it was blocking where it stood and which new lines it will block.

Remember that the computer's pawns act as walls too, and they can work for you. A light pawn standing on a line can stop the neutron short of the top row just as well as one of yours.

How the computer opponent plays

The computer always takes an immediate win if one exists. Otherwise its play depends on your streak in two ways:

• Search depth: with a streak of 0 or 1 it searches three turns ahead; from a streak of 2 onwards it searches four.
• Random moves: on some turns it skips the search and makes a random move that merely avoids sliding the neutron straight onto your home row. The chance starts at 80 percent and is multiplied by 0.7 for every win in your streak: about 39 percent at a streak of 2, 13 percent at 5, 2 percent at 10 and a fraction of a percent at 20. It keeps shrinking with every win and never levels off.

The four-turn search always runs to completion, however slow your device is, and takes well under a second even on an older phone, so the opponent is equally strong on every device. Deeper searches were tested and left out: under a reasonable time limit on a slow phone they played no better than the four-turn search.

The random moves at low streaks are not harmless gifts every time. The random pawn it moves can still close your route by accident, so keep checking the board rather than assuming the opponent is asleep.

Practical habits for a long streak

1. Read the neutron twice. First, where can it go now? Second, from the square you choose, where could the computer send it?
2. Use the highlighting. A marked winning square ends the round immediately, so always scan for one before thinking about anything else.
3. Block with distance. Place blockers in the middle of lines towards the top row, not just next to the neutron.
4. Hunt for the trap. When the neutron is near an edge, count its exits. If you can leave it with no safe slide for the computer, the round is yours.
5. Mind the turn limit. Rounds that drag on end as draws at 120 turns. A draw ends your streak just like a loss, so press while the position is in your favour.

Streaks and saving your score

Each round you win adds one to your streak and deals a new board; the first round you lose ends the game. Your best streak is stored on your device, and any streak above zero can be saved to the Hall of Fame from the game-over card. Pressing New in the middle of a game while your streak is above zero ends that game straight away, so you can still save the streak you had reached. By the tenth win the opponent almost never plays a random move, and from there each win makes its rare slips rarer still, so a long streak is where the real skill shows.