diff --git a/spec/building_spec.cr b/spec/building_spec.cr
new file mode 100644
index 0000000..9456a7a
--- /dev/null
+++ b/spec/building_spec.cr
@@ -0,0 +1,21 @@
+require "./spec_helper"
+
+describe Game::Building do
+  it "should create storehouse" do
+    bg = Game::Building.new Game::Building::Type::Storehouse, "Storehouse", storage: 100
+    bg.storage.should eq 100
+  end
+
+  it "should create crystal miner" do
+    bg = Game::Building.new Game::Building::Type::CrystalMiner, "Cryslal Miner", **{
+      production: Game::Production.new(
+        ts: 20,
+        input: Game::Resources.new,
+        output: Game::Resources.new({
+          Game::Resources::Type::Crystals => 100,
+        })
+      ),
+    }
+    bg.production.as(Game::Production).ts.should eq 20
+  end
+end
diff --git a/spec/command_spec.cr b/spec/command_spec.cr
new file mode 100644
index 0000000..634e916
--- /dev/null
+++ b/spec/command_spec.cr
@@ -0,0 +1,18 @@
+require "./spec_helper"
+
+describe Game::Command do
+  it "should complete build command" 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.free 10,
+    }
+    command = Game::BuildCommand.new point, building
+    world.push command
+    tile = world.map.get point
+    tile.should be_a(Game::ConstructionSiteTile)
+    world.run 10
+    tile = world.map.get point
+    tile.should be_a(Game::BuildingTile)
+  end
+end
diff --git a/spec/resources_spec.cr b/spec/resources_spec.cr
index 2770931..261e60c 100644
--- a/spec/resources_spec.cr
+++ b/spec/resources_spec.cr
@@ -1,8 +1,29 @@
 require "./spec_helper"
 
-describe Game::Resources do
-  it "should be created from hash" do
-    res = Game::Resources.new({Game::Resources::Type::Crystals => 100})
-    res[Game::Resources::Type::Crystals].should eq 100
+module Test::GameResources
+  alias Res = Game::Resources
+  alias ResType = Game::Resources::Type
+
+  describe Game::Resources do
+    it "should be created from hash" do
+      res = Res.new({ResType::Crystals => 100})
+      res[ResType::Crystals].should eq 100
+    end
+
+    it "should check single type" do
+      res = Res.new({ResType::Crystals => 100})
+      res.has(ResType::Crystals, 100).should be_true
+    end
+
+    it "should check resource bag" do
+      res = Res.new({ResType::Crystals => 100})
+      res.has({ResType::Crystals => 50}).should be_true
+      res.has({ResType::Crystals => 150}).should be_false
+    end
+
+    it "should check empty value" do
+      res = Res.new
+      res.has({ResType::Crystals => 50}).should be_false
+    end
   end
 end
diff --git a/src/game/building.cr b/src/game/building.cr
new file mode 100644
index 0000000..35c1f32
--- /dev/null
+++ b/src/game/building.cr
@@ -0,0 +1,74 @@
+module Game
+  struct Production
+    def initialize(@ts : TimeSpan, @input : Resources, @output : Resources)
+    end
+
+    getter ts
+    getter input
+    getter output
+  end
+
+  struct Restoration
+    def initialize(@ts : TimeSpan, @type : Resources::Type, @cap : Capacity)
+    end
+
+    getter ts
+    getter type
+    getter cap
+  end
+
+  struct Construction
+    def initialize(@ts : TimeSpan, @cost : Resources, @requirements : Array(Building::Type))
+    end
+
+    getter ts
+    getter cost
+    getter requirements
+
+    def self.immediatly
+      Construction.new 0, Resources.new, [] of Building::Type
+    end
+
+    def self.free(ts : TimeSpan)
+      Construction.new ts, Resources.new, [] of Building::Type
+    end
+  end
+
+  class Building
+    enum Role
+      Storehouse
+    end
+
+    enum Type
+      StartPoint
+      Storehouse
+      CrystalMiner
+      CrystalRestorer
+    end
+
+    def initialize(
+      @type : Type,
+      @name : String,
+      *,
+      roles : Array(Role) | Nil = nil,
+      construction : Construction | Nil = nil,
+      production : Production | Nil = nil,
+      restoration : Restoration | Nil = nil,
+      storage : Capacity | Nil = nil
+    )
+      @roles = roles.nil? ? Array(Role).new : roles
+      @construction = construction.nil? ? Construction.immediatly : construction.as(Construction)
+      @production = production
+      @restoration = restoration
+      @storage = storage.nil? ? 0 : storage
+    end
+
+    getter type
+    getter name
+    getter roles
+    getter construction
+    getter production
+    getter restoration
+    getter storage
+  end
+end
diff --git a/src/game/building_list.cr b/src/game/building_list.cr
new file mode 100644
index 0000000..1b7dcb0
--- /dev/null
+++ b/src/game/building_list.cr
@@ -0,0 +1,41 @@
+module Game
+  class BuildingList
+    def initialize
+      @items = [] of NamedTuple(t: Building::Type, b: Building)
+
+      add(
+        Building.new Building::Type::StartPoint, "Start Point", storage: 100
+      )
+
+      add(
+        Building.new Building::Type::CrystalMiner, "Crystal Miner", **{
+          production: Production.new(
+            ts: 20,
+            input: Resources.new,
+            output: Resources.new({
+              Resources::Type::Crystals => 100,
+            })
+          ),
+        }
+      )
+
+      add(
+        Building.new Building::Type::CrystalRestorer, **{
+          cost: Resources.new({
+            Resources::Type::Crystals => 100,
+          }),
+          restoration: Restoration.new(
+            ts: 30,
+            type: Resources::Type::Crystals,
+            cap: 50
+          ),
+        }
+      )
+    end
+
+    private def add(building : Building)
+      t = building.type
+      @items << {t: t, b: building}
+    end
+  end
+end
diff --git a/src/game/command.cr b/src/game/command.cr
index d264c48..4804d0a 100644
--- a/src/game/command.cr
+++ b/src/game/command.cr
@@ -2,18 +2,36 @@ require "./tile"
 
 module Game
   abstract class Command
-    abstract def start(world : World) : Int32
+    abstract def start(world : World) : TimeSpan
     abstract def finish(world : World)
     abstract def desc : String
   end
 
+  class BuildCommand < Command
+    def initialize(@point : Point, @building : Building)
+    end
+
+    def desc : String
+      sprintf "Building '%s'", building.name
+    end
+
+    def start(world : World) : TimeSpan
+      world.map.set(ConstructionSiteTile.new(@point))
+      @building.construction.ts
+    end
+
+    def finish(world : World)
+      world.map.set(BuildingTile.new(@point, @building))
+    end
+  end
+
   class BuildCrystalHarvesterCommand < Command
     BUILD_TIME = 30
 
     def initialize(@point : Point)
     end
 
-    def start(world : World) : Int32
+    def start(world : World) : TimeSpan
       tile = world.map.get(@point)
       if !tile.can_build?
         raise InvalidPlaceForBuilding.new
@@ -41,7 +59,7 @@ module Game
       @value = 0
     end
 
-    def start(world : World) : Int32
+    def start(world : World) : TimeSpan
       deposit_tile = nearest_deposit(world)
       stock_tile = nearest_stock(world)
       if deposit_tile && stock_tile
@@ -83,7 +101,7 @@ module Game
     def initialize(@point : Point)
     end
 
-    def start(world : World) : Int32
+    def start(world : World) : TimeSpan
       tile = world.map.get(@point)
       if !tile.can_build?
         raise InvalidPlaceForBuilding.new
@@ -113,7 +131,7 @@ module Game
     def initialize(@point : Point)
     end
 
-    def start(world : World) : Int32
+    def start(world : World) : TimeSpan
       @target_tile = nearest_deposit(world)
       if @target_tile
         dist = @point.distance(@target_tile.as(Tile).point)
@@ -148,7 +166,7 @@ module Game
     def initialize(@point : Point)
     end
 
-    def start(world : World) : Int32
+    def start(world : World) : TimeSpan
       tile = world.map.get(@point)
       if !tile.can_build?
         raise InvalidPlaceForBuilding.new
@@ -178,7 +196,7 @@ module Game
       @can_terr = false
     end
 
-    def start(world : World) : Int32
+    def start(world : World) : TimeSpan
       if world.resources.has(Resources::Type::Crystals, CRYSTAL_REQUIRED)
         world.resources.dec(Resources::Type::Crystals, CRYSTAL_REQUIRED)
         @can_terr = true
diff --git a/src/game/game.cr b/src/game/game.cr
new file mode 100644
index 0000000..eeb24e6
--- /dev/null
+++ b/src/game/game.cr
@@ -0,0 +1,5 @@
+module Game
+  alias TimePoint = Int64
+  alias TimeSpan = Int32 | Int64
+  alias Capacity = Int32
+end
diff --git a/src/game/resources.cr b/src/game/resources.cr
index e016596..b3c97e6 100644
--- a/src/game/resources.cr
+++ b/src/game/resources.cr
@@ -8,12 +8,17 @@ class Game::Resources
 
   alias Capacity = Int32
 
-  def initialize
-    @values = {} of Type => Capacity
-  end
+  alias ResourceBag = Hash(Type, Capacity)
 
-  def initialize(vals : Hash(Type, Capacity))
-    @values = vals.clone
+  def initialize(vals : ResourceBag | Nil = nil)
+    @values = {} of Type => Capacity
+    Type.each { |t, v| @values[t] = 0 }
+    if vals.is_a?(ResourceBag)
+      vals.each do |i|
+        t, v = i
+        @values[t] = v
+      end
+    end
   end
 
   def [](t : Type)
@@ -21,7 +26,15 @@ class Game::Resources
   end
 
   def has(t : Type, value : Capacity) : Bool
-    @values.fetch(t, 0) >= value
+    @values[t] >= value
+  end
+
+  def has(vs : ResourceBag) : Bool
+    vs.reduce true do |acc, entry|
+      t = entry[0]
+      v = entry[1]
+      acc && @values[t] >= v
+    end
   end
 
   def inc(t : Type, value : Capacity)
@@ -32,6 +45,14 @@ class Game::Resources
     @values[t] = new_value
   end
 
+  def inc?(vs : ResourceBag) : Bool
+    false unless has(vs)
+    vs.each do |t, c|
+      @values[t] = @values[t] + c
+    end
+    true
+  end
+
   def dec(t : Type, value : Capacity)
     inc(t, -value)
   end
diff --git a/src/game/tile.cr b/src/game/tile.cr
index aa0ae43..9b07243 100644
--- a/src/game/tile.cr
+++ b/src/game/tile.cr
@@ -7,6 +7,7 @@ module Game
     Plateau
     Terraformer
     Warehouse
+    Building
   end
 
   abstract class Tile
@@ -20,9 +21,12 @@ module Game
     getter cap
     getter cur
 
-    abstract def letter : Char
     abstract def has_role(role : TileRole) : Bool
 
+    def letter : Char
+      ' '
+    end
+
     def withdraw(value)
       if value >= @cur
         wd = @cur
@@ -118,4 +122,15 @@ module Game
       role == TileRole::Terraformer
     end
   end
+
+  class BuildingTile < Tile
+    def initialize(@point : Point, @building : Building)
+    end
+
+    def has_role(role : TileRole) : Bool
+      role == TileRole::Building
+    end
+
+    getter building
+  end
 end
diff --git a/src/game/world.cr b/src/game/world.cr
index 8da4a30..5416312 100644
--- a/src/game/world.cr
+++ b/src/game/world.cr
@@ -1,9 +1,9 @@
 require "./resources"
 
 class Game::World
-  property ts : Int64
+  property ts : TimePoint
 
-  def initialize(@map : Map, @ts = 0_i64)
+  def initialize(@map : Map, @ts : TimePoint = 0_i64)
     @start_ts = @ts
     @resources = Resources.new
     @queue = Queue.new
@@ -23,7 +23,7 @@ class Game::World
     @queue.push(done_at, command)
   end
 
-  def run(ts : Int64)
+  def run(ts : TimePoint)
     loop do
       item = @queue.pop(ts)
       if item.nil?