How to play Amir's Chess

• Two ways to play. A Quick Battle is one fight on one board. A Campaign is a world map where you take cities, raise armies and march on the enemy capital — and every attack opens a battle on that square's own ground.
• The one rule that changes everything. Your King moves like every piece type you still have on the board. Lose your last Rook and he stops sliding like a rook — that instant.
• So hunt his types, not his pieces. Taking one of two Rooks changes nothing about his King. Taking the second one disarms it.
• Winning. Checkmate wins a battle. Taking the enemy capital wins a campaign.

Your King always has his ordinary one-square move. On top of that he borrows moves from the piece types you still have on the board:

• Rook — he slides like a rook.
• Bishop — he slides like a bishop.
• Knight — he jumps like a knight.
• Queen — she counts as a rook and a bishop.
• Pawns give him nothing.
• Towers (the two immobile guns in a siege) count as Rooks for the defender.

Only pieces standing on the board count. Pieces waiting in reserve do not. Lose the last piece of a type and that power is gone at once, mid-move.

Because his powers can be switched off but his one-square move cannot, a King who is down to his last few pieces is a very different King from the one who started.

Phantom defence

Your King only truly defends a piece at contact — a square he can reach with his own one-square move.

Say your last Rook sits two squares away on a file, "defended" by your King's rook lines. Those lines exist because of that rook. Take it and the defence vanishes in the same instant, so it was never defended at all.

The same trap applies to your last Knight: no King can guard a knight at range unless he still has a knight, and a Queen does not grant the jump.

The rule of thumb: keep your last piece of a type beside your King, or do not count on him. And when attacking, take the second-to-last piece of a type first — the last one's defence becomes a phantom.

Checks cut both ways

A checking piece attacks along a line the King may own himself, so an unguarded checker can simply be taken by the King.

• A Rook checking down a file falls to a King who still has a Rook.
• A checking Knight falls to a King who still has a Knight.
• A checking pawn falls to his ordinary one-square move.

A check from a distance is only safe if the checker is defended — and beware defending it with your own King's power: if the checker is your last piece of its type, capturing it disarms that defence as it happens.

Checkmate wins, as in chess. But the King starts almost uncatchable, so the plan is to strip his army first.

Rout. A King whose last piece is taken — nothing on the board, nothing in reserve — is routed, and the battle ends at once, provided the enemy still has a piece of their own. It is judged on his move: if his King can still legally capture an enemy piece, the battle goes on, and it is judged again each time he is to move. So an unguarded last attacker next to him can still be taken; a guarded one cannot.

Draws: two bare Kings, stalemate, or the move budget running out (below).

A battle gets 50 moves. This is not a chess clock — there is no thinking time. It is a length limit so one fight cannot swallow the whole campaign, and the counter warns you when you are inside the last ten.

If it runs out, everyone still fighting is asked whether to fight on: one extension of 20 more moves, and everyone must agree. Against the computer, that means you decide alone.

If nobody extends, the battle is a draw:

• The attacker withdraws with every piece still standing — nothing is lost to the clock.
• The defender keeps the ground.
• The attacker cannot attack again next turn.

Only a voluntary retreat costs you pieces (see below).

You may retreat only when you are not in check.

• Pieces on your own half of the board survive, and so does everything in reserve.
• Pieces on the enemy half are lost — the price of having pushed forward.

In a campaign, a retreating army is shaken and cannot move on its next turn, and you choose where the survivors land (see Attacking on the map).

Pawns move as in chess: one square forward, capture diagonally, a double-step from their own second rank, and en passant.

On the last rank a pawn gets a battlefield promotion — Knight, Bishop or Rook. Never a Queen.

Promotion is worth more than the piece it makes: promoting to a type you have lost hands that power back to your King.

Each side fields at most three rows of pieces. Anything beyond that waits in reserve.

Instead of moving, you may tap a reserve piece and drop it on an empty square of your own back rank. That is your whole turn — and you may not drop while in check unless the drop itself resolves it.

Reserve pieces do not feed the King's powers. They only count once they are standing on the board.

Every battle happens on a piece of terrain, and the terrain changes how pieces move. In a campaign it is decided by the square you are fighting over.

Field

Open ground. Ordinary chess.

River

Rank 5 is water, except the fords at b, e and g. Sliding pieces cross only through a ford; knights leap only where the L-path lands on one.

Hill

Attacking sliders must stop when they climb onto ranks 6–8. The defender, already on the high ground, is unaffected. Knights climb freely.

Forest

Sliders of both sides stop when they enter ranks 4–5. Fighting in the trees is close work.

City walls (a siege)

• The wall runs along rank 5, with gates at c5 and f5 and two immobile Towers at d5 and e5.
• Towers capture like rooks, never move, and count as Rooks for the defending King. Capture a Tower to breach the wall.
• Knights cross only through a gate.
• Pawns may climb the wall from the square directly behind it, from either side. Up there only a pawn or a Tower can take them.
• A wall pawn may step down or capture off the wall as usual — losing that protection as it goes.
• A Tower sees along the whole wall until something blocks its line.

The world is itself a chessboard — 8×8 or 16×16 — painted with the ground you fight on. A battle happens on the square's own terrain, and a walled city is a siege.

Every world is generated fresh and is mirror-symmetric, so neither side gets the better start. You are White, in the west.

Two things are chosen once at setup and cannot be changed afterwards: whether the world has barbarians, and whether it has fog of war.

Take the enemy capital to win. Campaigns against the computer save themselves after every move — use Continue on the menu. Export save writes a JSON file you can carry to another device.

A world is made with fog unless you turn it off — it is chosen once, at setup, and cannot be changed later. With fog on, you see only what your own people can see, and so does your opponent: the computer has to scout as well.

What sees

• Every army of yours, and every square you hold — a city is an eye as well as a purse.
• Sight reaches two squares, or three from a hill.
• You cannot see into a forest unless you are standing next to it.
• Mountains block sight — nothing sees past a ridge, because nothing can go through one.
• You still see the ranges you stand beside — close enough to see the land is close enough to see the mountains on it — but not the ones across the world.

What you remember

Land is remembered; armies are not. Ground you have walked stays on your map — its terrain, its rivers, its walls. But who is standing there, who owns it now, and what its city is building are things you would have to go and look at again. A square you remember but cannot see is drawn dim; one nobody has ever walked to is blank.

The side panel and the turn log follow the same rule. You get your own gold, cities and army points; theirs read unknown, and the log stops narrating their turn. Battles are the exception — a battle is loud, and the whole map hears that one happened.

What changes in play

• You can march into a square you cannot see. If something is there, you find out the way armies always have.
• A raider riding two squares will not be turned back by an enemy it had no way of knowing about — it rides in and stops there.
• Rally points still work, and still stop when an enemy comes within two squares — but only an enemy you can actually see.

Fog is drawn on your own screen. In a hotseat game that means not peeking while your opponent takes their turn, and online it is a game between friends, not a sealed vault.

An army moves one square in any direction, once per turn. Mountains cannot be entered at all.

A move belongs to the pieces, not the square. March half an army out and the half left behind still has its own move this turn. When you march, a picker asks who goes — counters start at nobody, so detaching a single Pawn is one tap, and March all sends everyone.

Armies that meet on a square merge. An army that retreated from a battle is shaken and cannot move on its next turn.

The to-do line at the top of the map counts your unmoved armies and idle cities, and cycles through them. If an army is one you have looked at and want to leave alone, Set aside drops it out of that cycle for this turn only — you can still select and move it by hand.

• Cities earn gold every turn: a capital 5, a city 3.
• Every city you own also raises one Pawn per turn, free.
• Alongside that free Pawn, each city can build one piece at a time for its cost in gold: Knight or Bishop take 1 turn, Rook 2, Queen 5.
• Mines, farms and quarries add 2 gold a turn to whoever last stood on them — you claim one by walking onto it, and you keep it after you leave.

Cities and resources change hands by walking in. A city with nobody in it is simply taken.

Give an army a rally point and it marches one square toward it at the start of each of your turns, routing itself around mountains. Setting one is free and does not use the army's move.

You may set several from one square. Send one Pawn north and two Knights east from the same city — the button becomes Add rally point after the first, each order gets its own line with a ✕, and no piece can be promised to two places at once. Each detachment becomes an independent army the moment it steps out.

The orders stop themselves. If an enemy army comes within two squares, the order is cancelled, the army holds with its move unspent, and it turns up in the to-do line asking for a decision. A rally march never starts a battle — though it will walk into an undefended enemy city on the way, which can include an undefended capital.

An order also clears when the army arrives, when it is attacked, or when you march it somewhere that does not bring it closer. Nudging an army along by hand keeps the order; sending it the other way cancels it.

An army of nothing but Knights marches two squares a turn, and may attack on either step. Select one and the map lights up the two-away squares as well — one tap makes the whole ride.

It will not ride through an enemy army or an enemy city, but the far square may be either: a raider can cross open ground and strike in the same turn.

The trade: in the battle that follows, a Knights-only army gives its King only the knight jump — no rook or bishop lines. Fast on the map, brittle on the board.

Mixing ends it. Knights that merge into a stack with anything else march once, like everyone else.

Sieges

Attack a walled city the defender holds and the defender chooses: hold the walls (fight the siege board, with its Towers) or sally out (fight on open ground).

Where the survivors land

When a battle ends in a retreat, the retreating player picks the square: two squares from the battlefield, and never next to an enemy army. An army with nowhere legal to land is lost.

Overrun — battles that are already decided

Against the computer, an attack more than 2½ times the defence is settled on the map with no battle screen at all: the attacker takes the square, the defender falls back two squares, shaken. Nobody loses a piece — which is exactly what a played-out battle gives, since the defender would retreat on move one anyway.

A walled city counts its two Towers toward the defence, so a real garrison always gets its siege, and an army with nowhere to fall back to has to fight. In hotseat and online games there is no overrun: a human defender always gets the choice.

If the world was made with them — it is chosen once, at setup — rogue warbands answer to nobody and raid both sides.

• They come from camps. March an army onto an empty camp to raze it for good; leave it and it raises warbands all game.
• A warband is rabble next to a real army. But some are Knights only and cross two squares a turn, and their King moves like a Knight — awkward to corner if you have no knights left.
• They never take ground. A city they beat is sacked: you keep it, but it earns nothing, raises no free Pawn and finishes nothing for three rounds. A resource square they walk onto goes back to unclaimed.
• They cannot win the game — and killing them all is not a victory either.

Two players, one device. Both Quick Battle and Campaign offer hotseat: you pass the phone across.

Online. Both players open the page, type the same room code and join. The first to join is White — the attacker in a quick battle, the western kingdom in a campaign. A few spectators may watch. Either player may ask for a take-back, which the other accepts or declines.

Zoom. Use + and −, or pinch with two fingers on a phone. When you are zoomed in, the rank and file labels stay frozen along the edges, so you never lose your place.

Selection. Tap a square to select it; tap your army, then a neighbouring square, to march or attack. Tap a city you own to build.

The log at the side of the map lists what moved, what held and what was cancelled, every turn.

The world is alive. Birds cross the sky, cattle graze the pasture, deer startle in the trees and chimneys smoke in every town. None of it affects play — it is weather, not rules — and it turns itself off for anyone whose device asks for reduced motion.