diff --git a/heightmap.lua b/heightmap.lua
index e132283..1e7ae42 100644
--- a/heightmap.lua
+++ b/heightmap.lua
@@ -7,44 +7,44 @@ module(...)
 
 -- Find power of two sufficient for size
 local function pot(size)
-	local pot = 2
-	while true do
-		if size <= pot then return pot end
-		pot = 2*pot
-	end
+    local pot = 2
+    while true do
+        if size <= pot then return pot end
+        pot = 2*pot
+    end
 end
 
 -- Create a table with 0 to n zero values
 local function tcreate(n)
-	local t = {}
-	for i = 0, n do t[i] = 0 end
-	return t
+    local t = {}
+    for i = 0, n do t[i] = 0 end
+    return t
 end
 
 -- Square step
 -- Sets map[x][y] from square of radius d using height function f
 local function square(map, x, y, d, f)
-	local sum, num = 0, 0
-	if 0 <= x-d then
-		if   0 <= y-d   then sum, num = sum + map[x-d][y-d], num + 1 end
-		if y+d <= map.h then sum, num = sum + map[x-d][y+d], num + 1 end
-	end
-	if x+d <= map.w then
-		if   0 <= y-d   then sum, num = sum + map[x+d][y-d], num + 1 end
-		if y+d <= map.h then sum, num = sum + map[x+d][y+d], num + 1 end
-	end
-	map[x][y] = f(map, x, y, d, sum/num)
+    local sum, num = 0, 0
+    if 0 <= x-d then
+        if   0 <= y-d   then sum, num = sum + map[x-d][y-d], num + 1 end
+        if y+d <= map.h then sum, num = sum + map[x-d][y+d], num + 1 end
+    end
+    if x+d <= map.w then
+        if   0 <= y-d   then sum, num = sum + map[x+d][y-d], num + 1 end
+        if y+d <= map.h then sum, num = sum + map[x+d][y+d], num + 1 end
+    end
+    map[x][y] = f(map, x, y, d, sum/num)
 end
 
 -- Diamond step
 -- Sets map[x][y] from diamond of radius d using height function f
 local function diamond(map, x, y, d, f)
-	local sum, num = 0, 0
-	if   0 <= x-d   then sum, num = sum + map[x-d][y], num + 1 end
-	if x+d <= map.w then sum, num = sum + map[x+d][y], num + 1 end
-	if   0 <= y-d   then sum, num = sum + map[x][y-d], num + 1 end
-	if y+d <= map.h then sum, num = sum + map[x][y+d], num + 1 end
-	map[x][y] = f(map, x, y, d, sum/num)
+    local sum, num = 0, 0
+    if   0 <= x-d   then sum, num = sum + map[x-d][y], num + 1 end
+    if x+d <= map.w then sum, num = sum + map[x+d][y], num + 1 end
+    if   0 <= y-d   then sum, num = sum + map[x][y-d], num + 1 end
+    if y+d <= map.h then sum, num = sum + map[x][y+d], num + 1 end
+    map[x][y] = f(map, x, y, d, sum/num)
 end
 
 -- Diamond square algorithm generates cloud/plasma fractal heightmap
@@ -52,36 +52,36 @@ end
 -- Size must be power of two
 -- Height function f must look like f(map, x, y, d, h) and return h'
 local function diamondsquare(size, f)
-	-- create map
-	local map = { w = size, h = size }
-	for c = 0, size do map[c] = tcreate(size) end
-	-- seed four corners
-	local d = size
-	map[0][0] = f(map, 0, 0, d, 0)
-	map[0][d] = f(map, 0, d, d, 0)
-	map[d][0] = f(map, d, 0, d, 0)
-	map[d][d] = f(map, d, d, d, 0)
-	d = d/2
-	-- perform square and diamond steps
-	while 1 <= d do
-		for x = d, map.w-1, 2*d do
-			for y = d, map.h-1, 2*d do
-				square(map, x, y, d, f)
-			end
-		end
-		for x = d, map.w-1, 2*d do
-			for y = 0, map.h, 2*d do
-				diamond(map, x, y, d, f)
-			end
-		end
-		for x = 0, map.w, 2*d do
-			for y = d, map.h-1, 2*d do
-				diamond(map, x, y, d, f)
-			end
-		end
-		d = d/2
-	end
-	return map
+    -- create map
+    local map = { w = size, h = size }
+    for c = 0, size do map[c] = tcreate(size) end
+    -- seed four corners
+    local d = size
+    map[0][0] = f(map, 0, 0, d, 0)
+    map[0][d] = f(map, 0, d, d, 0)
+    map[d][0] = f(map, d, 0, d, 0)
+    map[d][d] = f(map, d, d, d, 0)
+    d = d/2
+    -- perform square and diamond steps
+    while 1 <= d do
+        for x = d, map.w-1, 2*d do
+            for y = d, map.h-1, 2*d do
+                square(map, x, y, d, f)
+            end
+        end
+        for x = d, map.w-1, 2*d do
+            for y = 0, map.h, 2*d do
+                diamond(map, x, y, d, f)
+            end
+        end
+        for x = 0, map.w, 2*d do
+            for y = d, map.h-1, 2*d do
+                diamond(map, x, y, d, f)
+            end
+        end
+        d = d/2
+    end
+    return map
 end
 
 -- Default height function
@@ -89,18 +89,18 @@ end
 -- h is mean height at map[x][y] (from square/diamond of radius d)
 -- returns h' which is used to set map[x][y]
 function defaultf(map, x, y, d, h)
-	return h + (random()-0.5)*d
+    return h + (random()-0.5)*d
 end
 
 -- Create a heightmap using the specified height function (or default)
 -- map[x][y] where x from 0 to map.w and y from 0 to map.h
 function create(width, height, f)
-	f = f and f or defaultf
-	-- make heightmap
-	local map = diamondsquare(pot(max(width, height)), f)
-	-- clip heightmap to desired size
-	for x = 0, map.w do for y = height+1, map.h do map[x][y] = nil end end
-	for x = width+1, map.w do map[x] = nil end
-	map.w, map.h = width, height
-	return map
+    f = f and f or defaultf
+    -- make heightmap
+    local map = diamondsquare(pot(max(width, height)), f)
+    -- clip heightmap to desired size
+    for x = 0, map.w do for y = height+1, map.h do map[x][y] = nil end end
+    for x = width+1, map.w do map[x] = nil end
+    map.w, map.h = width, height
+    return map
 end