only re-apply/generate flow field if we need to

src/game.lua

@@ -23,7 +23,7 @@ local TRDTS = {
 }
 
 local function get_initial_game_state(seed)
-    local STARTING_MONEY = 50
+    local STARTING_MONEY = 10000
     local map, world = random_map(seed)
 
     return {
@@ -130,15 +130,28 @@ local function game_action(scene)
     if WIN:mouse_pressed"left" then
         if interactable then
             if buildable then
+                local broken, flow_field = making_hex_unwalkable_breaks_flow_field(hex, tile)
                 local cost = get_tower_cost(state.selected_tower_type)
-                if cost > state.money then
+
+                if broken then
+                    local node = WIN.scene("cursor"):child(2)
+                    node.color = COLORS.CLARET
+                    node:action(am.tween(0.1, { color = COLORS.TRANSPARENT }))
+                    play_sfx(SOUNDS.BIRD2)
+
+                elseif cost > state.money then
                     local node = WIN.scene("cursor"):child(2)
                     node.color = COLORS.CLARET
                     node:action(am.tween(0.1, { color = COLORS.TRANSPARENT }))
                     play_sfx(SOUNDS.BIRD2)
+
                 else
                     update_money(-cost)
-                    build_tower(hex, state.selected_tower_type)
+                    build_tower(hex, state.selected_tower_type, flow_field)
+
+                    if flow_field then
+                        apply_flow_field(state.map, flow_field, state.world)
+                    end
                 end
             end
         end

src/grid.lua

@@ -54,18 +54,17 @@ function tile_is_medium_elevation(tile)
     return tile.elevation >= -0.5 and tile.elevation < 0.5
 end
 
--- map elevation to appropriate color
 function color_at(elevation)
-    if elevation < -0.5 then -- lowest elevation
+    if elevation <= -0.5 then -- lowest elevation
         return COLORS.WATER{ a = (elevation + 1.4) / 2 + 0.2 }
 
-    elseif elevation < 0 then -- med-low elevation
+    elseif elevation <= 0 then -- med-low elevation
         return math.lerp(COLORS.DIRT, COLORS.GRASS, elevation + 0.5){ a = (elevation + 1.8) / 2 + 0.3 }
 
-    elseif elevation < 0.5 then -- med-high elevation
+    elseif elevation <= 0.5 then -- med-high elevation
         return math.lerp(COLORS.DIRT, COLORS.GRASS, elevation + 0.5){ a = (elevation + 1.6) / 2 + 0.3 }
 
-    elseif elevation < 1 then     -- high elevation
+    elseif elevation <= 1 then     -- high elevation
         return COLORS.MOUNTAIN{ ra = elevation }
     end
 end
@@ -74,17 +73,6 @@ function grid_heuristic(source, target)
     return math.distance(source, target)
 end
 
-function making_hex_unwalkable_breaks_flow_field(hex, tile)
-    local original_elevation = tile.elevation
-    -- making the tile's elevation very large *should* make it unwalkable
-    tile.elevation = 999
-
-    local flow_field = generate_flow_field(state.map, HEX_GRID_CENTER)
-    local result = not hex_map_get(flow_field, 0, 0)
-    tile.elevation = original_elevation
-    return result, flow_field
-end
-
 function grid_cost(map, from, to)
     local t1, t2 = map.get(from.x, from.y), map.get(to.x, to.y)
 
@@ -102,9 +90,7 @@ function generate_flow_field(map, start)
     return dijkstra(map, start, nil, grid_cost)
 end
 
-function generate_and_apply_flow_field(map, start, world)
-    local flow_field = generate_flow_field(map, start)
-
+function apply_flow_field(map, flow_field, world)
     local flow_field_hidden = world and world"flow_field" and world"flow_field".hidden or true
     if world and world"flow_field" then
         world:remove"flow_field"
@@ -136,6 +122,21 @@ function generate_and_apply_flow_field(map, start, world)
     end
 end
 
+function making_hex_unwalkable_breaks_flow_field(hex, tile)
+    if not mob_can_pass_through(nil, hex, tile) then
+        return false
+    end
+
+    local original_elevation = tile.elevation
+    -- making the tile's elevation very large *should* make it unwalkable
+    tile.elevation = 999
+
+    local flow_field = generate_flow_field(state.map, HEX_GRID_CENTER)
+    local result = not hex_map_get(flow_field, 0, 0)
+    tile.elevation = original_elevation
+    return result, flow_field
+end
+
 function random_map(seed)
     local map = rectangular_map(HEX_GRID_DIMENSIONS.x, HEX_GRID_DIMENSIONS.y, seed)
     math.randomseed(map.seed)
@@ -197,7 +198,7 @@ function random_map(seed)
         end)
     end
 
-    generate_and_apply_flow_field(map, HEX_GRID_CENTER, world)
+    apply_flow_field(map, generate_flow_field(map, HEX_GRID_CENTER), world)
 
     return map, am.translate(WORLDSPACE_COORDINATE_OFFSET) ^ world
 end

src/mob.lua

@@ -25,7 +25,7 @@ end
 -- check if a the tile at |hex| is passable by |mob|
 function mob_can_pass_through(mob, hex)
     local tile = state.map.get(hex.x, hex.y)
-    return tile and tile_is_medium_elevation(tile)
+    return tile_is_medium_elevation(tile)
 end
 
 function mob_die(mob, mob_index)

src/tower.lua

@@ -330,13 +330,18 @@ function make_and_register_tower(hex, tower_type)
     if tower_type == TOWER_TYPE.REDEYE then
     elseif tower_type == TOWER_TYPE.LIGHTHOUSE then
         tower.perimeter = ring_map(tower.hex, tower.range)
+        local tile = state.map.get(hex.x, hex.y)
+        tile.elevation = tile.elevation + 0.5
 
     elseif tower_type == TOWER_TYPE.WALL then
+        state.map.get(hex.x, hex.y).elevation = 0.5
+
     elseif tower_type == TOWER_TYPE.MOAT then
+        state.map.get(hex.x, hex.y).elevation = -0.49
+
     elseif tower_type == TOWER_TYPE.RADAR then
     end
 
-    generate_and_apply_flow_field(state.map, HEX_GRID_CENTER, state.world)
     register_entity(TOWERS, tower)
 end