Hexagon has water now: rivers, lakes, the sea, underground streams. You swim them instead of walking, the current carries off whatever stops swimming, and a river can have a bridge over it. The first rivers are in Reinos de Leyenda: Aeternum, one of the games built on Hexagon.

The rules come from the system of oceans and seas I wrote for Ciudad Capital in 2009, ported and extended. They live in two shared files, lib/room/water.c and lib/room/coast.c. A game still made of rooms inherits them through the room bases /lib/water.c and /lib/coast.c. A game on locations gets the same rules from the water and coast components, and converting a room to a location attaches the component with the room’s own settings, so rooms and locations run the same code.

World map with a river drawn in blue between the forest and Naduk

The world map of Reinos de Leyenda: Aeternum, with the Anduin in blue. Each cell of the world map stands for 10×10 locations of the game.

Water and coasts

A water location says which way the water flows, how hard, and what happens to a swimmer going against it:

set_water_current(DIR_SOUTHEAST);        // the exit the water flows out by
set_water_strength(2);                   // 0 still .. 3 rapids
set_water_upstream(WATER_UPSTREAM_HARD); // free | hard | block
set_water_depth(2);                      // 1 surface, 2 deep

Its edges are coasts: a beach, a cliff, a port, a river bank. A coast declares its kind and nothing else.

The ways into, across and out of the water are swum exits. A swum exit belongs to the map and to the coordinate graph like any other, and the map draws water as [~], but it is not listed with the exits and typing its direction does nothing. The path finder leaves it out unless whoever walks it can swim. Every exit of a water location is swum, and on a coast you mark the ones that go into the water with the swim option of add_exit.

Swimming

Players get across with the swim skill, and anybody who reaches water or a coast learns it. From a coast, swim on its own goes into the water. Once you are in, the location shows no exit lines. It says where the shore is and every way you can swim:

> swim south
~ You start swimming.
You manage to swim towards the south.

You can see the shore towards the west. You can swim towards the north, the south and the west.

Going in from a coast always works. Every stroke after that is rolled against the swimmer’s ability. Going with the current makes it easier; crossing it gets harder the stronger it runs, and against a hard current harder still, while nobody swims against a block one. Deep water makes it harder, and so does carrying more than half of what the swimmer can bear.

Whoever fails a stroke swallows water and loses a bite of life, never the last of it, and the current takes them downstream. Whoever stays in moving water without swimming is carried off after a while anyway. That is the easy way down a river:

You let yourself go and the current sweeps you away.

Then the next location, and a while later the next one.

What the current carries

Each drag also rolls a chance of being thrown against the rocks, higher the stronger the current and lower the better the swimmer. The harm grows with the strength of the current and with the victim’s own life, so a strong river hurts anybody:

The current batters you against the rocks and drags you under.

It can kill, and the death happens in the water: the ghost stays where it died, and the current drags ghosts too. A ghost cannot swim, but it walks the swum exits by typing the direction, as a spirit.

Items go the same way. Anything that is not a living and can be picked up is carried off when it lies in a location with a current. Each location keeps a single call_out, armed when the first item arrives, and moves everything that arrived by then in one pass. Items dropped together reach the next location together. On every drag each item rolls once:

  • it can be lost for good, unless it is or holds a unique item, which the water never takes;
  • it can be washed onto the shore, if that location has a swum exit to a coast;
  • otherwise it goes on downstream and is queued again there.

Someone who dies in the water leaves the gear out of the corpse, money and worn items included, and each piece drifts on its own, like the corpse, so your clothes, your armour or anything else you carried can end up on a bank further down, or be lost for good.

NPCs keep out of the water unless their template says swims. A fish walks the swum exits and finds paths through them, and it is the only kind of NPC an area places in a water location.

Bridges

A bridge is one location at one coordinate that is land and water at once. It carries every water setting, plus exits of type bridge, which are walked. Its other exits are swum, except a road across it, which stays a road.

Each living in that location is in one of two positions, on the bridge or in the water. You arrive on the bridge, unless you came in through a swum exit or were put in the water by a jump or a fall. On the bridge nothing drifts and only the bridge exits work. In the water the location reads like any other water: the shore line, the swim directions, the drift. jump drops you off the bridge into the river, and while you are in the water under a bridge you can reach, the location says so:

> jump into the river
You jump from the bridge into the water.

You can swim towards the northeast and the south. You are passing under a bridge, try to 'climb'.

climb gets you back up with a climb roll, which gets harder the stronger the current.

A bridge can be too high (set_bridge_reachable(0)). Then there is no climbing up, and no fighting between the two positions either: the attack command and aggressive NPCs both ask the location query_out_of_reach(attacker, victim) before a fight starts. On a low bridge someone on the deck and someone in the water can fight each other.

In a room it is one more base and one more exit type:

inherit "/lib/bridge.c";

set_water_current(DIR_SOUTH);
set_water_strength(1);
add_exit(DIR_EAST, <bank>, "bridge");     // walked
add_exit(DIR_NORTH, <water>, "standard"); // swum, as in any water

A location needs only the bridge component, in place of the water one. Other code asks query_in_water(who) of the location, and can drop somebody through a breaking plank with drop_into_water().

On the maps

The local map marks both kinds of cell, and its legend says what they are. This is the local map seen from the abandoned bridge over the Anduin, in the Orgoth forest:

Local map seen from the bridge cell: water and bridge cells along the river, with the legend for shore, water and bridge

The local map seen from the abandoned bridge, where the star stands. The bridge drawn upstream is Gyneth’s bridge; the water cells and the shore have glyphs of their own.

On the world map rivers are drawn per sector, the way roads are, in blue box lines, as in the map at the top of this post. A sector records the swum exits of every water location with a current in it, and a line is drawn only between two water locations; still water, with no current, draws no line. Where a straight road crosses a straight river in the same sector, the map shows a crossing glyph.

The source code is in the Hexagon repository.