Make ghosts pass terrain and die on purgatory

Ghosts no longer collide with terrain, but die on collision with the
ghost purgatory tile in the graveyard.

.vscode/settings.json

@@ -22,6 +22,8 @@
         "lighting_dist",
         "crown_bar",
         "rest_sound",
-        "won"
+        "won",
+        "ghost_collision_map",
+        "ghost_death_sound"
     ]
 }

main.lua

@@ -41,6 +41,8 @@ end
 
 function love.load()
     --BACKGROUND_COLOUR = Colour.construct(71, 45, 60)
+    GHOST = 321
+    GRAVEYARD_PURGATORY = 591
     BACKGROUND_COLOUR = Colour.construct(0, 0, 0)
     TILE_SIZE = 16
     DEBUG_ENABLED = false
@@ -75,6 +77,9 @@ function love.load()
     rest_sound:setVolume(0.5)
     rest_sound:setPitch(0.5)
 
+    ghost_death_sound = love.audio.newSource("assets/ghost_death.wav", "static")
+    ghost_death_sound:setVolume(0.75)
+
     local walk_sound = love.audio.newSource("assets/walk.wav", "static")
     walk_sound:setVolume(0.2)
 
@@ -123,7 +128,8 @@ function love.load()
     shader = love.graphics.newShader(require("src/shader"))
     tileset = SpriteSheet.load_sprite_sheet("assets/kenney_1-bit-pack/Tilesheet/colored_packed.png", TILE_SIZE, TILE_SIZE)
     tilemap = require "assets/map"
-    collision_map = TileMap.construct_collision_map(tilemap, "terrain")
+    collision_map = TileMap.construct_collision_map(tilemap, "terrain", function(tile_index) return tile_index == 0 end) -- passable if empty
+    ghost_collision_map = TileMap.construct_collision_map(tilemap, "terrain", function(tile_index) return true end) -- always passable
     tiles = TileMap.construct_tiles(tilemap, tileset)
     entities = Entity.construct_from_tilemap(
         tiles["enemies"].tiles,
@@ -206,7 +212,13 @@ local function update(dt)
     end
 
     for _, entity in ipairs(entities) do
-        entity:update(dt, player, collision_map)
+        local x, y = unpack(entity:get_current_tile())
+        local tile = tiles["terrain"]:get(x, y)
+        if not entity.dead and tile and tile.index == GRAVEYARD_PURGATORY and entity.tile.index == GHOST then
+            entity:die()
+            ghost_death_sound:play()
+        end
+        entity:update(dt, player, entity.tile.index == GHOST and ghost_collision_map or collision_map)
     end
 
     if not player:check_alive() then

src/entity.lua

@@ -16,6 +16,7 @@ function Entity.construct(args)
         y = args.y,
         tile = args.tile,
         target = nil,
+        dead = false,
     }
 
     function entity.get_current_tile(self)
@@ -24,6 +25,10 @@ function Entity.construct(args)
         return {x, y}
     end
 
+    function entity.die(self)
+        self.dead = true
+    end
+
     function entity.walk_to_target(self, current_tile, dt)
         if not self.walk_sound:isPlaying() then
             self.walk_sound:play()
@@ -39,6 +44,10 @@ function Entity.construct(args)
     end
 
     function entity.update(self, dt, player, collision_map)
+        if self.dead then
+            return
+        end
+
         local current_tile = self:get_current_tile()
         if self.target then
             self:walk_to_target(current_tile, dt)
@@ -77,6 +86,10 @@ function Entity.construct(args)
     end
 
     function entity.render(self, camera)
+        if self.dead then
+            return
+        end
+
         local transform = love.math.newTransform(self.x - camera.total_x, self.y - camera.total_y)
         love.graphics.draw(self.tileset.image, self.tile.quad, transform)
         -- if self.walk_animation.ongoing then

src/tilemap.lua

@@ -56,7 +56,7 @@ function TileMap.construct_tiles(tilemap, tileset)
 end
 
 -- for use with luafinding a 2d table of bools (passable or not)
-function TileMap.construct_collision_map(tilemap, layer_name)
+function TileMap.construct_collision_map(tilemap, layer_name, passable_getter)
     local tiles = {}
     local width = tilemap.width
     for _, layer in ipairs(tilemap.layers) do
@@ -67,7 +67,7 @@ function TileMap.construct_collision_map(tilemap, layer_name)
         for i, tile_index in ipairs(layer.data) do
             local x = i % width
             local y = math.floor(i / width)
-            tiles[x][y] = tile_index == 0 --passable if empty
+            tiles[x][y] = passable_getter(tile_index)
         end
         ::continue::
     end