diff --git a/src/command.cr b/src/command.cr
index 9f4dca3..9ddc219 100644
--- a/src/command.cr
+++ b/src/command.cr
@@ -16,8 +16,7 @@ class BuildCrystalHarvesterCommand < Command
   end
 
   def finish(world : World)
-    harverster = CrystalHarvesterTile.new(@point)
-    world.map.set(harverster)
+    world.map.set(CrystalHarvesterTile.new(@point))
     world.push(HarvestCrystalCommand.new(@point))
   end
 end
@@ -45,7 +44,7 @@ class HarvestCrystalCommand < Command
   end
 
   def finish(world : World)
-    world.resources.add_crystal(@value)
+    world.resources.inc(ResourceType::Crystal, @value)
     world.push(HarvestCrystalCommand.new(@point))
   end
 
diff --git a/src/expansion.cr b/src/expansion.cr
index ee92af6..99adf8e 100644
--- a/src/expansion.cr
+++ b/src/expansion.cr
@@ -3,16 +3,25 @@ require "./command"
 require "./map"
 require "./queue"
 
+enum ResourceType
+  Crystal
+  Terraformation
+end
+
 class Resources
-  def initialize(@crystal = 0)
+  def initialize
+    @values = {} of ResourceType => Int32
+    ResourceType.each do |t|
+      @values[t] = 0
+    end
   end
 
-  def add_crystal(x)
-    @crystal += x
+  def [](t : ResourceType)
+    @values[t]
   end
 
-  def crystal
-    @crystal
+  def inc(t : ResourceType, value : Int32)
+    @values[t] = @values[t] + value
   end
 end
 
@@ -64,4 +73,4 @@ w.push(BuildCrystalRestorerCommand.new(Point.new(1, 2)))
 w.push(BuildCrystalRestorerCommand.new(Point.new(3, 2)))
 w.run(60)
 w.map.print
-printf "Wood: %d\n", w.resources.crystal
+pp w.resources