diff --git a/index_map.md b/index_map.md
new file mode 100644
index 0000000..da118b2
--- /dev/null
+++ b/index_map.md
@@ -0,0 +1,38 @@
+### sprites
+---
+### map tiles
+2 - grass
+3 - bush
+4 - tree
+5 - red flowers
+6 - pink flowers
+7 - mushrooms
+8 - big mushroom
+9 - sand
+10 - cactus with flower
+11 - pebbles
+12 - rock
+13 - cactus
+14 - tree stump
+15 - cactus stump
+16 - mushroom stump
+17 - long grass
+
+### inventory icons
+65 - wood
+66 - mushroom
+67 - cactus meat
+
+### sfx
+---
+0 - noise effect for wind track (sfx 9)
+1 - little bell
+8 - desert music 1
+9 - desert wind
+10 - desert music 2
+11 - chopping wood
+12 - chopping vegetation
+
+### patterns
+---
+0-1 - desert bgm (loops on 1)
diff --git a/mapgen.lua b/mapgen.lua
index 87059c6..fd693fe 100644
--- a/mapgen.lua
+++ b/mapgen.lua
@@ -7,20 +7,7 @@ function init_mapgen()
 
    -- Metadata for different biomes
    -- frequencies don't have to add up to 100, but they should by convention
-   --
-   -- Sprites are:
-   --  * 2 - grass
-   --  * 3 - bush
-   --  * 4 - tree
-   --  * 5 - red flowers
-   --  * 6 - pink flowers
-   --  * 7 - mushrooms
-   --  * 8 - big mushroom
-   --  * 9 - sand
-   --  * 10 - cactus with flower
-   --  * 11 - pebbles
-   --  * 12 - rock
-   --  * 13 - cactus
+   -- tile_frequencies tuples are {frequency, sprite_index}, see index_map.md
    biome_data = {
       grassland = {
          biome_frequency = 75,
@@ -92,17 +79,17 @@ end
 
 -- determines which biome a given world map position should be,
 -- returns the object out of the biome_data table
-function get_biome(pos)
+function get_biome_name(pos)
    local biome_pos = calculate_biome_pos(pos)
    local uid = generate_uid(biome_pos)
-   local biome_name = biome_metadata[(uid % #biome_metadata) + 1]
-   return biome_data[biome_name]
+   return biome_metadata[(uid % #biome_metadata) + 1]
 end
 
 -- determine what sprite to render for a given position.
 -- todo: this needs the ability to have a list of 'changed' tiles to check against.
 function get_tile(pos)
-   local biome = get_biome(pos)
+   local biome_name = get_biome_name(pos)
+   local biome = biome_data[biome_name]
    local uid = generate_uid(pos)
 
    return biome["tile_lookup"][(uid % #biome["tile_lookup"]) + 1]
diff --git a/player.lua b/player.lua
index 837f85f..361e2e5 100644
--- a/player.lua
+++ b/player.lua
@@ -88,6 +88,15 @@ end
 function draw_player()
    spr(player_lookup[facing[1]][facing[2]], 64, 64)
    -- todo: animate the character on move
+
+   -- draw the player's HUD
+   if fget(mget(player_pos[1], player_pos[2]), 1) then
+      -- flag 1 represents an interactable (read: destructible) sprite.
+      -- need a map of destructible map objects, appropriate sfx, replacement
+      -- sprites.
+   end
+
+   -- todo: introduce the concept of an inventory here
 end
 
 -- pos is camera position, meaning the map-relative player
diff --git a/sfx_map.md b/sfx_map.md
deleted file mode 100644
index 912155c..0000000
--- a/sfx_map.md
+++ /dev/null
@@ -1,12 +0,0 @@
-### sfx
----
-0 - noise effect for wind track (sfx 9)
-1 - little bell
-
-8 - desert music 1
-9 - desert wind
-10 - desert music 2
-
-### patterns
----
-0-1 - desert bgm (loops on 1)