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Keelhold

Stow crates along the deck and keep the barge level. Ship matching lots, and mind the lurch when they lift!

Goal

You are loading a barge. Seven hatches run across her deck, and each one sits a fixed distance from the keel, so a crate dropped into an outer hatch leans her over and a crate dropped into the middle one does not. Trim is that lean as a single whole number: negative to port, positive to starboard. Keep it inside the voyage's tolerance and she rides level; take it outside and she is listing, and the next crate has to bring her back. Crates arrive three at a time, each with a weight and a cargo type, and you choose which hatch each one goes into. Gather a manifest's worth of one cargo type in a single hatch and the whole lot ships out at once, which pays you and, because the weight leaves the hull in one beat, throws the trim the other way. That is the lurch, and it is the game: you are balancing a hull that keeps changing under you. Ship the voyage's quota of lots and you make port, where you may cast off on a harder voyage or stop and keep the score you have. There is no last voyage. The run ends when she goes over, when there is nowhere left to put the crate in hand, or when you decide you have gone far enough.

Scoring

Higher is better, and the score only ever goes up: nothing in the game subtracts, and a run that goes badly simply stops adding. Every award is scaled by the voyage multiplier M, which is the voyage number plus 3, so the same work is worth more the further you have come. Shipping a lot pays floor(10 * W * A * C * M / 32), where W is the total weight of everything that left the hull on that hook including any iron ballast riding out with it, A is the hatch's lever award (4 at the keel, then 5, 6, 8 and 10 as the hatches step outward), and C is the chain: 2 for one shipping turn, then 3, 4, 5, 6, 7 and 8 for each consecutive shipping turn after it, held at 8. A turn that ships nothing resets the chain, so the next lot starts again at 2. Three flat awards sit on top, each paid at floor(base * M / 4): 75 for righting her, paid when she began the turn listing and ends it back inside the tolerance; 50 for an even keel, paid when a lot shipped and the trim finished within 3 of level; and 150 for every rush crate that shipped on or before its due turn, paid once per crate, so a lot carrying two of them pays it twice. Completing a voyage pays 300 times the voyage number. Stopping at port pays nothing extra and costs nothing: you keep exactly the score you have.

Rules

THE HULL. Seven hatches, indexed 0 to 6 in state and in every action, and the number a player sees is one higher, so hatch index 3 is the one labelled Hatch 4 and it sits on the keel. Their lever arms are -3, -2, -1, 0, +1, +2 and +3 by default, and the keel hatch's arm is always 0 whatever else changes. On voyage 1 the two outermost hatches are shut and only five are in use; from voyage 2 every hatch is open. Each hatch holds up to params.capacity crates and keeps them in arrival order. TRIM. trim = params.wind + the sum over every crate aboard of crate.weight * its hatch's arm. It is a whole number, always exact, and state.trim is that sum recomputed after every change. She is listing while the absolute value of trim is strictly greater than params.tolerance, and state.listing is that reading as it stood at the start of the current turn. THE QUEUE. state.queue holds the crates you have been handed, nearest first, and queue[0] is the crate in hand: the only one a PLACE can place. Each crate carries a whole weight and either a cargo type (a small number, one of params.cargoTypes kinds) or null, which is iron ballast: it belongs to no manifest and can never complete one, but it weighs the same as anything else and it rides out with the next lot to leave its hatch. Some voyages send a rush crate, which carries rushWindow; the clock starts when you place it, not when you are handed it, and crate.due is then the turn it must ship by. A rush crate that misses its due turn does not end anything: it turns into iron ballast where it lies, keeping its weight. ACTIONS. Exactly three. { "type": "PLACE", "bay": 0 to 6 } while state.phase is loading, { "type": "CAST_OFF" } and { "type": "END_RUN" } while it is port, and nothing at all once it is over. A PLACE is legal when the hatch is open, is not jammed at the current turn and is below capacity; getLegalActions returns exactly those, so you never have to work legality out. THE TURN. Placing the crate in hand does all of this in order: the wind flips if a squall is due, the crate lands in the hatch you named and the trim is recomputed, then the manifest resolves. If that hatch now holds params.manifestSize crates of the placed crate's cargo type, they ship as a lot together with every piece of iron ballast in that hatch, the weight leaves the hull in one beat and the trim is recomputed again. That second recomputation is the lurch, and it is what makes a good placement dangerous: the crate that completes the lot removes far more weight than it added. Then the awards are paid on the trim as it finished, any rush crate past its due turn becomes iron ballast, a hatch may jam, the queue refills, and the run is checked. SAFETY, AND THE ONE THING TO READ CAREFULLY. state.safeBays lists the hatches where placing the crate in hand does not end the run, and state.listingBays is the subset of those that leave her listing afterwards. Both are computed by the engine by resolving the whole turn on a throwaway copy, so they are exact rather than an estimate, and they are published to a browser and to this API identically: neither side has information the other does not. THEY ARE AN ADVISORY, NOT A RESTRICTION. A PLACE on a hatch that is legal but not in safeBays is accepted and applied in full, and it is how runs end: it leaves her in a position the rules count as swamped, and the run is over the moment no hatch at all is safe for the crate then in hand. A later crate can sometimes still rescue her from there, and often cannot. If you want to survive, place into safeBays. THE GRACE, once, on the turn it is earned: if she was level at the start of the turn and your placement both ships a lot and leaves her listing, that is allowed, because the lot's lurch is what pushed her over and you get exactly the next crate to bring her back inside. If she was already listing at the start of the turn, only a hatch that ends the turn back inside the tolerance is safe. A placement that tips her over without shipping anything is not safe either. The run ends at the check that follows a placement, whenever safeBays comes back empty for the new crate in hand: with cause lurch if she was listing, noSafeStow if she was level, and holdFull if no hatch was even legal. JAMS. On some voyages a hatch jams every params.jamEvery turns, chosen at random from the open hatches, never the keel hatch and never one already jammed, and it refuses crates until state.turn reaches its jammedUntil. At most params.maxJams are shut at once, and casting off clears every one of them. THE PORT CALL. Ship params.quota lots and state.phase becomes port. There state.castOffSafe tells you whether the crate in hand would still have a safe stow under the next voyage's terms, which matters because the hold, the queue and the crate ids all carry over untouched: nothing is emptied at port. CAST_OFF commits the next voyage, which raises the tolerance and the quota, opens every hatch, clears every jam, refills the crate bags under the new cargo count and weight range, and applies the new wind, which state.next has been showing you since the voyage began. From voyage 21 a voyage also carries conditions, drawn from a fixed set and never repeating the previous voyage's: squall flips the wind every few turns, longBoom widens the outer arms to -4 and +4, shortCrew shows you one fewer crate ahead, heavyLot adds a point of weight to everything, tightWater narrows the tolerance, rushSeason and ballastRun tighten those cadences, and stickyHatches jams more often and allows two jams at once. They are served as identifiers, exactly as state.params.conditions carries them. END_RUN, accepted at port only, ends the run there and lets you keep the current score. It pays no bonus and it forfeits nothing, so stopping is never worth more or less than the score you already have; it is there so a good run can be kept without having to be thrown away first. DETERMINISM. The whole run replays from state.seed and your action list. A refused action costs nothing at all: no turn, no crate, no movement of the random cursor, and the state you get back is the one you sent. There is a hard guard at 20,000 placements, which ends a run the same way END_RUN does.

Action grammar

{
  "type": "object",
  "oneOf": [
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "PLACE",
          "description": "Put the crate in hand into a hatch. Legal only while phase is loading."
        },
        "bay": {
          "type": "integer",
          "minimum": 0,
          "maximum": 6,
          "description": "The hatch index, 0 to 6, where 3 is the keel hatch and carries no lever arm. A hatch outside state.safeBays is still a legal target and ends the run."
        }
      },
      "required": [
        "type",
        "bay"
      ],
      "additionalProperties": false
    },
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "CAST_OFF",
          "description": "Sail on to the next voyage. Accepted only while phase is port. It keeps the hold, the queue and the score, opens every hatch, clears every jam and applies the terms state.next has been showing."
        }
      },
      "required": [
        "type"
      ],
      "additionalProperties": false
    },
    {
      "type": "object",
      "properties": {
        "type": {
          "const": "END_RUN",
          "description": "Stop at port and keep the current score. Accepted only while phase is port. It pays no bonus, forfeits nothing and moves no random cursor."
        }
      },
      "required": [
        "type"
      ],
      "additionalProperties": false
    }
  ]
}

Start a game

curl -s "https://gameboard.gg/api/games/keelhold/init?seed=7"

Then POST { stateToken, action } to https://gameboard.gg/api/games/keelhold/action, carrying the stateToken forward each call. See the API overview for the full loop.