Everything the game does, in the order it does it.

The battlefield

One shared grid covers both banks and the water between them — a single coordinate space for the whole match. Its atomic unit is the Tile: placement, damage and enclosure are all reasoned about per tile.

Every tile is either land or water, and terrain is fixed for the whole match. Nothing changes it.

Home Ground is the region a player may build on. It is fixed at the start and never changes hands. You may place blocks and cannons only on your own ground; when a player is eliminated, theirs is scored for nobody and nobody may build on it.

What stands on it

The clock

Time is counted in ticks at 30 a second. Both players are inside the same phase at the same instant; nothing pauses.

Nomination is not part of any round. A round is Battle → Build → Cannon, so the first thing anyone does in a round is fire. The last round’s trailing Cannon Phase does not run: score is already paid, and no battle follows it.

The Battle Phase does not end at its timer. At the timer it reaches cease-fire: no new fire is accepted, but everything already in the air still lands, and the phase ends only once the last one has. No damage ever falls outside the phase that caused it.

Each round two things get harder: the build timer shrinks, and the block supply shifts toward larger, more awkward shapes. The second is the bigger lever.

Nomination

Every castle on the board stands bare, with no walls anywhere. Each player picks one on their own ground as their Home Castle, under a 10-second timer, and is then given a starting wall and an opening cannon grant.

The Build Phase

Players place blocks to repair and extend their walls. A player who ends it holding no enclosed castle is eliminated.

One polyomino arrives at a time, from a shuffled bag drawn in order rather than sampled at random — so a round’s supply is something you can reason about. There is no queue and no lookahead. The bag is rebuilt at the start of every Build Phase from that round’s composition, which is what makes the escalation exact.

Placement — overlap only

A block may go wherever every tile it covers is on the board, is within the placing player’s own ground, is land, and is clear of wall, castle, cannon and rubble. Nothing else blocks it. A bonus square may be built over.

Enclosure

Enclosure is decided by flooding inward from every tile on the board’s edge, moving only up, down, left and right — never diagonally — and blocked by wall, water, castle and cannon. Any land tile the flood cannot reach is enclosed. It asks only whether the outside can reach in; it never traces wall loops, which is how it handles thickness, branching and coastline with no special cases.

When the timer expires there is a 4-second grace period, and then everything is settled at once: enclosure, territory, score, and who is still in the match.

The Cannon Phase

The Battle Phase

Both players fire at each other’s walls, in real time, simultaneously.

Firing

You aim at a tile and fire. You never name a cannon and you never name a target player. The game picks the next eligible cannon in the order they were placed, skipping any that is destroyed, cut off, silenced, or already has a ball in the air — skipping, never waiting.

So your oldest guns are your most reliable, and both your firing rate and your firing positions were set by an ordering chosen several rounds ago. A cannon may have only one ball in the air at a time, so your rate of fire is bounded by how many cannons you hold.

Flight

Everything about a shot is decided the moment it is fired — where it lands and when. Nothing is revised in flight and nothing can be intercepted; the arc is only how a decided outcome is shown.

The blast

A landing shell damages a fixed five-tile plus: the tile it hits and the four directly above, below, left and right. It destroys wall on those tiles, leaving clear, buildable ground, and it applies wherever it falls — open ground, already-destroyed wall, or the firing player’s own bank. There is no “did it hit a wall” test, so a shot landing one tile short genuinely chips the edge of what it was aimed at.

Castles are immune. Nothing can destroy a castle, ever.

A plus rather than a square, because against one-tile-thick wall the two are identical, and they diverge against double-thick wall: a plus removes four tiles and leaves a hole where a square would breach cleanly. Spending blocks on depth instead of width is a real strategy, and the plus is the shape that rewards it.

Hitting a cannon

Territory

Territory is recomputed from scratch at the end of every Build Phase and held unchanged until the next one. It is written by exactly two events: the end of a Build Phase, and nomination, once.

The Build Phase boundary is deliberately the damper. Recomputing live would punish a breach instantly and non-locally — one tile destroyed at a thin isthmus can silence a battery nowhere near the impact, with nothing on screen to explain it. A breach is punished, but only after its owner has had a phase to repair it.

Score

Paid at the end of every Build Phase and nowhere else, and banked permanently. A round that loses ground earns less; it never gives back what earlier rounds paid.

Ending a match

A player who ends a Build Phase holding no enclosed castle, while another does, is eliminated. It is immediate and final — no lives, no continues. Their walls, castles and cannons stay where they stand and go inert: the guns never fire again, the ground is scored for nobody, and no survivor may build on it.

Failing to enclose is the only way to lose. Castles are immune to fire precisely so that this stays true.

Controls

There are exactly six things you can ask for.

Bindings as they currently stand — these are not fixed:

The game is playable with no pointing device at all — nothing in the scheme requires a mouse, and trackpads are common enough that nothing important is bound to a right button alone. Touch is out of scope deliberately rather than deferred: the Build Phase wants a precise pointer while the clock runs, and a finger hides the tile it is placing on.

The mouse is captured — hidden and locked to the window — which is what makes relative motion available. Losing that capture does not pause the match. The game keeps running behind whatever resume prompt appears; freezing is never something a player can invoke.