feat: add Streaks.new, Streaks.record and Terrain.slide

src/terrain.lua

@@ -0,0 +1,49 @@
+-- Permanent map terrain that punishes careless movement, as opposed to
+-- hazards.lua's fire and gas which are timed and spawned mid-game. Lava
+-- scorches whoever stands on it every time they step there, a chasm drops
+-- the player to the floor below (or swallows a monster outright), and ice
+-- keeps sliding a traveller in the direction they started moving until
+-- something stops them. None of it spreads, fades, or needs saving beyond
+-- the glyph already baked into the map by the builder.
+
+local Tiles = require("tiles")
+local Status = require("status")
+local Resistances = require("resistances")
+
+local Terrain = {}
+
+Terrain.LAVA_DAMAGE = 8
+
+-- Slides entity through consecutive ice tiles in direction (dx, dy), from
+-- wherever it just came to rest. Stops the instant the current tile isn't
+-- ice, the next cell is unwalkable, or another actor already occupies it -
+-- so ice never carries a traveller through a wall or on top of someone else.
+function Terrain.slide(level, entity, dx, dy)
+  local map = level.map
+  while map:get(entity.x, entity.y) == Tiles.ICE do
+    local nx, ny = entity.x + dx, entity.y + dy
+    if not map:isWalkable(nx, ny) then break end
+    if level:entityAt(nx, ny) then break end
+    entity.x, entity.y = nx, ny
+  end
+end
+
+-- Applies lava's burn to whoever is currently standing on it. Returns a log
+-- line, or nil when the tile underfoot isn't lava.
+function Terrain.afflictLava(level, entity)
+  if level.map:get(entity.x, entity.y) ~= Tiles.LAVA then return nil end
+  local dealt = Resistances.apply(entity, Terrain.LAVA_DAMAGE, Resistances.FIRE)
+  entity.hp = entity.hp - dealt
+  if dealt <= 0 then
+    return entity.kind == "player" and "you wade through the lava unharmed"
+      or string.format("%s wades through the lava unharmed", entity.name)
+  end
+  Status.apply(entity, Status.BURNING, 2, math.max(1, dealt // 3))
+  return string.format("molten rock sears %s for %d", entity.name, dealt)
+end
+
+function Terrain.isChasm(level, entity)
+  return level.map:get(entity.x, entity.y) == Tiles.CHASM
+end
+
+return Terrain