Towline — Hook the barges, berth them in reverse

What is Towline — Hook the barges, berth them in reverse

Towline gives you a tug, a square of water and a handful of barges that want to go home. Sail over a barge and it hooks on right behind you, following your wake cell by cell. Each barge has a colour and each berth carries the colour of one of them, but a berth only takes the barge closest to the tug — the last one you picked up. That single rule turns a delivery job into a planning problem, because you never choose the drop order directly. You choose it backwards, at the moment you decide what to hook.

The second rule is geometric. Towed barges sit on real cells, so the line behind you is a moving wall you cannot sail through, and rocks and the shore are walls too. As the tow grows to four or five barges the free water shrinks, and it becomes easy to close off a pocket you can never enter again. Fuel falls by one every move and each delivery returns four, so a route that wanders is a route that runs dry. Clear every barge to bank the fuel you saved, and match par for a bonus on top.

How to play

1. Move the tug one cell at a time: arrow keys or WASD on a computer; on a phone, swipe or tap a cell next to it.
2. Sail onto a barge to hook it. It attaches directly behind the tug, and the whole line then follows the exact path you sail.
3. Reaching a berth releases only the barge nearest the tug, and only if the colours match; a wrong colour costs the move and nothing more.
4. Clear every barge to finish the harbour. Each move burns one unit of fuel, and the run ends at zero fuel or with no legal move left.

Strategies that work

• Berths are on the board from the first move, so plan the drops before the pickups. A berth releases only the barge nearest the tug, so your delivery order is the exact reverse of your hooking order. Hook first the barge whose berth you mean to visit last.
• The tow line is only the cells the barges occupy, not your whole wake, so four barges under tow make a five-cell wall that travels with you. Rocks and the shore are walls too, and once the chain reaches them it seals off a pocket of water you cannot re-enter until the tow shortens.
• A delivery pays 100 points plus 40 for every other barge still on the line, so a drop made while towing five is worth 260. Leftover fuel pays twelve a unit and a move costs one, so a detour of four moves already costs more than the extra barge it collects.
• Par is not an estimate. Every harbour is built by tracing a full solution first, and par is the length of that route, so it is always reachable and matching it already pays 250 points plus 25 per harbour. Three under-par harbours in a row unlock Precision Pilot.
• Nothing stops you towing every barge at once, and the Flotilla award asks for six, but each harbour is shaped around a shorter line: two barges early, three from harbour three, four from six, five from ten. Past that you are steering a snake the water was not cut for.

A little history

Towline was written for this site. Its ordering rule is the stack — last in, first out — the same object that sits under Shunt's railway sidings, but the two games ask opposite questions. Shunt asks which sequences a siding can produce; here the sequence is yours to choose and the difficulty is where the stack lives. The tow is a path that never crosses itself, so the constraint that bites is the one Camille Jordan stated in the 1880s: a simple closed curve splits the plane into an inside and an outside. Sorting becomes a matter of geometry.

Frequently asked questions