Rework the game to use double-sized sprites. This gives us more room for detail.

world.lua

@@ -2,6 +2,24 @@
 --- environment
 
 function init_world()
+   -- constants for map tiles' sprite locations, as long as we have the
+   -- tokens
+   tile_tree = 1
+   tile_tree_stump = 3
+   tile_bush = 5
+   tile_empty_bush = 7
+   tile_cactus = 9
+   tile_flowering_cactus = 11
+   tile_cactus_stump = 13
+   tile_big_mushroom = 32
+   tile_mushroom_stump = 34
+   tile_pebbles = 36
+   tile_long_grass = 38
+   tile_red_flowers = 40
+   tile_pink_flowers = 42
+   tile_fairy_ring = 44
+   tile_rock = 46
+   
    -- Metadata for different biomes
    -- tile_frequencies tuples are {frequency, sprite_index}, see index_map.md
    -- frequencies by convention add up to 1000, but this is arbitrary, the
@@ -9,19 +27,51 @@ function init_world()
    biome_data = {
       meadow = {
          biome_frequency = 20,
-         tile_frequencies = { {525, 2}, {200, 5}, {200, 6}, {55, 18}, {19, 3}, {1, 4} }
+         base_color = 3,
+         tile_frequencies = {
+            {525, 0},
+            {200, tile_red_flowers},
+            {200, tile_pink_flowers},
+            {55,  tile_long_grass},
+            {19,  tile_bush},
+            {1,   tile_tree}
+         }
       },
       grassland = {
          biome_frequency = 55,
-         tile_frequencies = { {500, 2}, {345, 18}, {4, 3}, {1, 4}, {100, 5}, {50, 6} }
+         base_color = 3,
+         tile_frequencies = {
+            {500, 0},
+            {345, tile_long_grass},
+            {4, tile_bush},
+            {1, tile_tree},
+            {100, tile_red_flowers},
+            {50, tile_pink_flowers}
+         }
       },
       forest = {
          biome_frequency = 20,
-         tile_frequencies = { {600, 2}, {200, 4}, {50, 3}, {50, 5}, {40, 7}, {59, 6}, {1, 8} }
+         base_color = 3,
+         tile_frequencies = {
+            {600, 0},
+            {200, tile_tree},
+            {50, tile_bush},
+            {50, tile_red_flowers},
+            {40, tile_mushrooms},
+            {59, tile_pink_flowers},
+            {1, tile_big_mushroom}
+         }
       },
       desert = {
          biome_frequency = 5,
-         tile_frequencies = { {800, 9}, {109, 11}, {60, 13}, {30, 12}, {1, 10} },
+         base_color = 9,
+         tile_frequencies = {
+            {800, 0},
+            {109, tile_pebbles},
+            {60, tile_cactus},
+            {30, tile_rock},
+            {1, tile_flowering_cactus}
+         }
       }
    }
 
@@ -45,39 +95,35 @@ function init_world()
       build_biome(biome, biome_data[biome])
    end
 
-   -- the indices here are sprite numbers.
    object_interaction_map = {
-      -- bush
-      [3] = {
-         replacement = 17,
+      [tile_bush] = {
+         replacement = tile_empty_bush,
          sfx = 13,
          drop = 68
       },
 
-      -- tree
-      [4] = {
-         replacement = 14,
+      [tile_tree] = {
+         replacement = tile_tree_stump,
          sfx = 11,
          drop = 64
       },
 
-      -- big mushroom
-      [8] = {
-         replacement = 16,
+      [tile_big_mushroom] = {
+         replacement = tile_mushroom_stump,
          sfx = 12,
          drop = 65
       },
 
       -- cactus w/ flower
-      [10] = {
-         replacement = 15,
+      [tile_flowering_cactus] = {
+         replacement = tile_cactus_stump,
          sfx = 12,
          drop = 67
       },
 
       -- cactus
-      [13] = {
-         replacement = 15,
+      [tile_cactus] = {
+         replacement = tile_cactus_stump,
          sfx = 12,
          drop = 66
       }
@@ -95,9 +141,17 @@ end
 -- this calculates everything about the world fresh every frame,
 -- but pico-8 handles this just fine!
 function draw_world(start_x, start_y)
-   for x=0,15 do
-      for y=0,15 do
-         spr(get_tile(start_x-8+x, start_y-8+y), x*8, y*8)
+   for x=0,7 do
+      for y=0,7 do
+         -- color the background for this segment
+         rectfill(x*16, y*16, x*16+16, y*16+16,
+                  get_base_color(start_x-4+x, start_y-4+y))
+
+         -- now get the sprite, and render as long as it isn't 0
+         local sprite = get_tile(start_x-4+x, start_y-4+y)
+         if sprite ~= 0 then
+            spr(sprite, x*16, y*16, 2, 2)
+         end
       end
    end   
 end
@@ -141,8 +195,13 @@ function get_biome_name(pos_x, pos_y)
    return biome_metadata[(uid % #biome_metadata) + 1]
 end
 
+-- get the background color for the current biome
+function get_base_color(x, y)
+   local biome = get_biome_name(x, y)
+   return biome_data[biome].base_color
+end
+
 -- determine what sprite to render for a given position.
--- pos_x and pos_y are global coordinates.
 function get_tile(pos_x, pos_y)
    -- lookup changes in the change buffer
    local modded_sprite = mod_buffer[get_mod_key(pos_x, pos_y)]