diff --git a/spec/command_spec.cr b/spec/command_spec.cr
index 634e916..378b22b 100644
--- a/spec/command_spec.cr
+++ b/spec/command_spec.cr
@@ -15,4 +15,22 @@ describe Game::Command do
     tile = world.map.get point
     tile.should be_a(Game::BuildingTile)
   end
+
+  it "should restrict build if not enought resources" do
+    world = Game::World.new create_map_2x2
+    point = Game::Point.new 1, 0
+    building = Game::Building.new Game::Building::Type::StartPoint, "Dummy", **{
+      construction: Game::Construction.new(
+        ts: 10,
+        cost: Game::Resources.new({
+          Game::Resources::Type::Crystals => 100,
+        }),
+        requirements: [] of Game::Building::Type
+      ),
+    }
+    command = Game::BuildCommand.new point, building
+    expect_raises(Game::NotEnoughtResources) do
+      world.push(command)
+    end
+  end
 end
diff --git a/src/game/building.cr b/src/game/building.cr
index 35c1f32..dc6e40d 100644
--- a/src/game/building.cr
+++ b/src/game/building.cr
@@ -1,5 +1,5 @@
 module Game
-  struct Production
+  class Production
     def initialize(@ts : TimeSpan, @input : Resources, @output : Resources)
     end
 
@@ -8,7 +8,7 @@ module Game
     getter output
   end
 
-  struct Restoration
+  class Restoration
     def initialize(@ts : TimeSpan, @type : Resources::Type, @cap : Capacity)
     end
 
@@ -17,7 +17,7 @@ module Game
     getter cap
   end
 
-  struct Construction
+  class Construction
     def initialize(@ts : TimeSpan, @cost : Resources, @requirements : Array(Building::Type))
     end
 
diff --git a/src/game/command.cr b/src/game/command.cr
index 4804d0a..f7bcd9d 100644
--- a/src/game/command.cr
+++ b/src/game/command.cr
@@ -16,8 +16,13 @@ module Game
     end
 
     def start(world : World) : TimeSpan
+      construction = @building.construction
+      if !world.resources.has(construction.cost)
+        raise NotEnoughtResources.new
+      end
+      # @todo check requirements
       world.map.set(ConstructionSiteTile.new(@point))
-      @building.construction.ts
+      construction.ts
     end
 
     def finish(world : World)
diff --git a/src/game/resources.cr b/src/game/resources.cr
index b3c97e6..b794dc1 100644
--- a/src/game/resources.cr
+++ b/src/game/resources.cr
@@ -6,10 +6,10 @@ class Game::Resources
     Terraformation
   end
 
-  alias Capacity = Int32
-
   alias ResourceBag = Hash(Type, Capacity)
 
+  @values : ResourceBag
+
   def initialize(vals : ResourceBag | Nil = nil)
     @values = {} of Type => Capacity
     Type.each { |t, v| @values[t] = 0 }
@@ -37,6 +37,10 @@ class Game::Resources
     end
   end
 
+  def has(vs : self) : Bool
+    has vs.to_hash
+  end
+
   def inc(t : Type, value : Capacity)
     new_value = @values.fetch(t, 0) + value
     if new_value < 0
@@ -56,4 +60,8 @@ class Game::Resources
   def dec(t : Type, value : Capacity)
     inc(t, -value)
   end
+
+  def to_hash : ResourceBag
+    @values.clone
+  end
 end