diff --git a/build_levels.lua b/build_levels.lua
index 1ea0962..d6b1117 100644
--- a/build_levels.lua
+++ b/build_levels.lua
@@ -12,13 +12,16 @@ local function write_layer(layer, level_id)
 	local data = layer.data
 	io.write("const Tile tiles_", level_id, "_", layer.name, "[] = {\n")
 	for _, v in ipairs(data) do
-		io.write(v - 1, ",")
+		if v ~= 0 then
+			v = v - 1
+		end
+		io.write(v, ",")
 	end
 	io.write("};\n")
 end
 
 local function write_level(level, level_id)
-	solid_layer = -1
+	solid_layer = 1
 	-- write every layer
 	for i, layer in ipairs(level.layers) do
 		if layer.name == "solid" then