diff --git a/.travis.yml b/.travis.yml
index 523725d..cda070f 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -2,7 +2,7 @@ sudo: false
 language: scala
 jdk: openjdk11
 scala:
-  - 2.11.6
+  - 2.13.1
 script: sbt test site
 notifications:
   email:
diff --git a/build.sbt b/build.sbt
index 57c7102..564630a 100644
--- a/build.sbt
+++ b/build.sbt
@@ -6,12 +6,13 @@ name := "Keter"
 
 version := "0.0.1"
 
-scalaVersion := "2.11.12"
+scalaVersion := "2.13.1"
 
 libraryDependencies ++= Seq(
-  "com.lihaoyi" %%% "utest" % "0.3.1",
-  "org.scala-js" %%% "scalajs-dom" % "0.8.0",
-  "org.webjars" % "rot.js" % "0.5.0"
+  "com.lihaoyi" %%% "utest" % "0.7.2",
+  "org.scala-js" %%% "scalajs-dom" % "0.9.8",
+  "org.webjars" % "rot.js" % "0.5.0",
+  "org.scala-lang.modules" %%% "scala-collection-contrib" % "0.2.1"
 )
 
 npmDependencies in Compile += "rot-js" -> "0.6.2"
@@ -33,8 +34,8 @@ site := {
   import java.nio.file.{Files, StandardCopyOption}
   (webpack in fullOptJS in Compile).value
   val targetDirectory = target.value / sitePath.value
-  val sourceJS = target.value / "scala-2.11" / "scalajs-bundler" / "main" / "keter-opt-bundle.js"
-  val sourceMap = target.value / "scala-2.11" / "scalajs-bundler" / "main" / "keter-opt-bundle.js.map"
+  val sourceJS = target.value / "scala-2.13" / "scalajs-bundler" / "main" / "keter-opt-bundle.js"
+  val sourceMap = target.value / "scala-2.13" / "scalajs-bundler" / "main" / "keter-opt-bundle.js.map"
   val targetJS = targetDirectory / "keter.js"
   val targetMap = targetDirectory / sourceMap.name
   targetJS.mkdirs()
diff --git a/project/plugins.sbt b/project/plugins.sbt
index 2b2ef90..41de966 100644
--- a/project/plugins.sbt
+++ b/project/plugins.sbt
@@ -1,3 +1,3 @@
-addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.25")
+addSbtPlugin("org.scala-js" % "sbt-scalajs" % "0.6.31")
 
-addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler" % "0.14.0")
+addSbtPlugin("ch.epfl.scala" % "sbt-scalajs-bundler-sjs06" % "0.16.0")
diff --git a/src/main/scala/ru/org/codingteam/keter/game/IEngine.scala b/src/main/scala/ru/org/codingteam/keter/game/IEngine.scala
index aa08519..da34509 100644
--- a/src/main/scala/ru/org/codingteam/keter/game/IEngine.scala
+++ b/src/main/scala/ru/org/codingteam/keter/game/IEngine.scala
@@ -2,5 +2,5 @@ package ru.org.codingteam.keter.game
 
 
 trait IEngine {
-  def addMessage(msg: String)
+  def addMessage(msg: String): Unit
 }
diff --git a/src/main/scala/ru/org/codingteam/keter/game/Location.scala b/src/main/scala/ru/org/codingteam/keter/game/Location.scala
index 881bc2e..4871068 100644
--- a/src/main/scala/ru/org/codingteam/keter/game/Location.scala
+++ b/src/main/scala/ru/org/codingteam/keter/game/Location.scala
@@ -95,7 +95,7 @@ object Location extends Logging {
         submap = submap1,
         coords = skel1.coordsOf('@').coords,
         subspaceMatrix = SubspaceMatrix.identity),
-      items = Set(Knife("Knife"))
+      items = Set(Knife("Knife"), Knife("Knife"), Knife("Knife"))
     )
 
     val scp = human(
diff --git a/src/main/scala/ru/org/codingteam/keter/game/objects/EventQueue.scala b/src/main/scala/ru/org/codingteam/keter/game/objects/EventQueue.scala
index 838e83b..2753491 100644
--- a/src/main/scala/ru/org/codingteam/keter/game/objects/EventQueue.scala
+++ b/src/main/scala/ru/org/codingteam/keter/game/objects/EventQueue.scala
@@ -6,7 +6,7 @@ import scala.collection.SortedMap
 sealed class EventQueue(val timestamp: Double, events: SortedMap[Double, Seq[ScheduledEvent]]) {
 
   def addEvent(at: Double, event: ScheduledEvent): EventQueue = {
-    new EventQueue(timestamp, events + (at -> (events.getOrElse(at, IndexedSeq()) :+ event)))
+    new EventQueue(timestamp, events ++ Map(at -> (events.getOrElse(at, IndexedSeq()) :+ event)))
   }
 
   def nextEventTime: Option[Double] = events.headOption map (_._1)
@@ -19,7 +19,7 @@ sealed class EventQueue(val timestamp: Double, events: SortedMap[Double, Seq[Sch
     require(events.nonEmpty, "Event queue is empty!")
     events.head match {
       case (at, Seq(action)) => new EventQueue(timestamp, events.tail)
-      case (at, actions) => new EventQueue(timestamp, events.tail + (at -> actions.tail))
+      case (at, actions) => new EventQueue(timestamp, events.tail ++ Map(at -> actions.tail))
     }
   }
 
@@ -29,5 +29,7 @@ sealed class EventQueue(val timestamp: Double, events: SortedMap[Double, Seq[Sch
 }
 
 object EventQueue {
+  import Ordering.Double.IeeeOrdering
+
   val empty = new EventQueue(0, SortedMap())
 }
diff --git a/src/main/scala/ru/org/codingteam/keter/game/objects/Inventory.scala b/src/main/scala/ru/org/codingteam/keter/game/objects/Inventory.scala
index efaf507..3270ee1 100644
--- a/src/main/scala/ru/org/codingteam/keter/game/objects/Inventory.scala
+++ b/src/main/scala/ru/org/codingteam/keter/game/objects/Inventory.scala
@@ -14,5 +14,5 @@ case class Inventory(body: Set[Bodypart], equipment: Set[EquipmentItem], backpac
   /**
    * @return list of all inventory items either equipped or not.
    */
-  def allEquipment = equipment ++ backpack
+  def allEquipment: Set[EquipmentItem] = equipment ++ backpack
 }
diff --git a/src/main/scala/ru/org/codingteam/keter/game/objects/equipment/items/Weapon.scala b/src/main/scala/ru/org/codingteam/keter/game/objects/equipment/items/Weapon.scala
index aabaae1..f164017 100644
--- a/src/main/scala/ru/org/codingteam/keter/game/objects/equipment/items/Weapon.scala
+++ b/src/main/scala/ru/org/codingteam/keter/game/objects/equipment/items/Weapon.scala
@@ -11,8 +11,7 @@ abstract class Weapon extends EquipmentItem {
   def damage: Int
 }
 
-case class Knife(name: String,
-                 damage: Int = 50) extends Weapon {
+class Knife(private val _name: String, private val _damage: Int) extends Weapon {
 
   val cooldown = 200
   val missCooldown = 100
@@ -37,4 +36,14 @@ case class Knife(name: String,
 
   override val requires: Set[Capability] = Set(ManipulatorCapability)
 
+  override def damage: Int = _damage
+
+  /**
+   * Name of equipment item.
+   */
+  override def name: String = _name
+}
+
+object Knife {
+  def apply(name: String, damage: Int = 50) = new Knife(name, damage)
 }
diff --git a/src/main/scala/ru/org/codingteam/keter/map/package.scala b/src/main/scala/ru/org/codingteam/keter/map/package.scala
index be83abc..4324098 100644
--- a/src/main/scala/ru/org/codingteam/keter/map/package.scala
+++ b/src/main/scala/ru/org/codingteam/keter/map/package.scala
@@ -137,6 +137,8 @@ package object map {
     }
 
     def nextEvent: Option[(Double, ScheduledEvent, UniverseSnapshot)] = {
+      import Ordering.Double.IeeeOrdering
+
       val delays = (globalEvents.nextEventDelay map ((_, this))).toIndexedSeq ++
         actors.values.flatMap(a => a.nextEventDelay.map((_, a)))
       log.debug(s"Timestamp: ${globalEvents.timestamp}; First event count: ${delays.size}")
@@ -148,7 +150,7 @@ package object map {
             val (nextTimestamp, nextAction) = globalEvents.nextEvent.get
             val nextUniverse = copy(
               globalEvents = globalEvents.dropNextEvent().addTime(delay),
-              actors = actors.mapValues(_.addTime(delay)))
+              actors = actors.view.mapValues(_.addTime(delay)).toMap)
             log.debug(s"Event from universe, delay=$delay, next timestamp=$nextTimestamp")
             (nextTimestamp, nextAction, nextUniverse)
           case (delay, actor: ActorLike) =>
@@ -156,7 +158,7 @@ package object map {
             val nextAction = actor.eventQueue.nextEvent.get._2
             val nextUniverse = copy(
               globalEvents = globalEvents.addTime(delay),
-              actors = actors.mapValues(_.addTime(delay))).updatedActor(actor.id)(_.dropNextEvent())
+              actors = actors.view.mapValues(_.addTime(delay)).toMap).updatedActor(actor.id)(_.dropNextEvent())
             log.debug(s"Event from actor, delay=$delay, next timestamp=$nextTimestamp")
             (nextTimestamp, nextAction, nextUniverse)
         })
diff --git a/src/main/scala/ru/org/codingteam/keter/scenes/inventory/InventoryViewModel.scala b/src/main/scala/ru/org/codingteam/keter/scenes/inventory/InventoryViewModel.scala
index 826f5c3..aa3ea30 100644
--- a/src/main/scala/ru/org/codingteam/keter/scenes/inventory/InventoryViewModel.scala
+++ b/src/main/scala/ru/org/codingteam/keter/scenes/inventory/InventoryViewModel.scala
@@ -2,10 +2,11 @@ package ru.org.codingteam.keter.scenes.inventory
 
 import ru.org.codingteam.keter.game.objects.Inventory
 import ru.org.codingteam.keter.game.objects.equipment.EquipmentCategory._
-import ru.org.codingteam.keter.game.objects.equipment.{EquipmentCategory, EquipmentItem}
+import ru.org.codingteam.keter.game.objects.equipment.{Capability, EquipmentCategory, EquipmentItem}
 import ru.org.codingteam.keter.ui.viewmodels.{ItemsViewModel, StaticTextViewModel}
 import ru.org.codingteam.keter.util.VectorMap
 
+import scala.collection.mutable
 import scala.concurrent.Promise
 
 class InventoryViewModel(var inventory: Inventory) {
@@ -33,20 +34,31 @@ class InventoryViewModel(var inventory: Inventory) {
 
   val currentFolderItems = new ItemsViewModel[EquipmentItem](toVectorMap(inventory.allEquipment.toSeq)) {
 
+    def canEquip(item: EquipmentItem): Boolean = {
+      val inventoryProvidedCapabilities = inventory.body.foldLeft(mutable.MultiSet[Capability]())(_ ++= _.provides)
+      val inventoryRequiredCapabilities = inventory.equipment.foldLeft(mutable.MultiSet[Capability]())(_ ++= _.requires)
+
+      inventoryProvidedCapabilities --= inventoryRequiredCapabilities
+      (item.requires & inventoryProvidedCapabilities.toSet) == item.requires
+    }
+
     def equipped(item: EquipmentItem): Boolean = {
       inventory.equipment.contains(item)
     }
 
-    def toggleSelected() = {
+    def toggleSelected(): Unit = {
       selectedItem foreach { item =>
         var backpack = inventory.backpack
         var equipment = inventory.equipment
+
         if (equipped(item)) {
           equipment -= item
           backpack += item
-        } else {
+        } else if (canEquip(item)) {
           backpack -= item
           equipment += item
+        } else {
+          return
         }
 
         inventory = inventory.copy(backpack = backpack, equipment = equipment)
@@ -58,6 +70,6 @@ class InventoryViewModel(var inventory: Inventory) {
 
   private def toVectorMap(items: Seq[EquipmentItem]): VectorMap[EquipmentItem, String] = {
     val itemsWithNames = items.map(equipment => (equipment, equipment.name))
-    VectorMap(itemsWithNames.toSeq: _*)
+    VectorMap(itemsWithNames: _*)
   }
 }
diff --git a/src/test/scala/ru/org/codingteam/keter/game/actions/ChangeInventoryActionTest.scala b/src/test/scala/ru/org/codingteam/keter/game/actions/ChangeInventoryActionTest.scala
index 752a694..c4be00f 100644
--- a/src/test/scala/ru/org/codingteam/keter/game/actions/ChangeInventoryActionTest.scala
+++ b/src/test/scala/ru/org/codingteam/keter/game/actions/ChangeInventoryActionTest.scala
@@ -10,8 +10,8 @@ object ChangeInventoryActionTest extends TestSuite {
   val universe = Location.createLocation()
   val action = InventoryChangeAction(Inventory(Set(Head("h", 10)), Set(Knife("k")), Set()))
 
-  val tests = TestSuite {
-    'shouldChangeInventory {
+  val tests = Tests {
+    test("shouldChangeInventory") {
       val newState = action.perform(universe.playerId.get, universe)
       val player = newState.player.get
 
diff --git a/src/test/scala/ru/org/codingteam/keter/game/actions/WaitActionTest.scala b/src/test/scala/ru/org/codingteam/keter/game/actions/WaitActionTest.scala
index 2d85a62..cb8c778 100644
--- a/src/test/scala/ru/org/codingteam/keter/game/actions/WaitActionTest.scala
+++ b/src/test/scala/ru/org/codingteam/keter/game/actions/WaitActionTest.scala
@@ -9,8 +9,8 @@ object WaitActionTest extends TestSuite {
   val universe = UniverseSnapshot(Map(), Some(playerId), EventQueue.empty)
   val action = WaitAction(50.0)
 
-  val tests = TestSuite {
-    'shouldWait {
+  val tests = Tests {
+    test("shouldWait") {
       val newState = action.perform(playerId, universe)
       assert(newState == universe)
     }
diff --git a/src/test/scala/ru/org/codingteam/keter/game/objects/InventoryTest.scala b/src/test/scala/ru/org/codingteam/keter/game/objects/InventoryTest.scala
new file mode 100644
index 0000000..f1e66a9
--- /dev/null
+++ b/src/test/scala/ru/org/codingteam/keter/game/objects/InventoryTest.scala
@@ -0,0 +1,16 @@
+package ru.org.codingteam.keter.game.objects
+
+import ru.org.codingteam.keter.game.objects.equipment.items.Knife
+import utest._
+
+import scala.collection.MultiSet
+
+object InventoryTest extends TestSuite {
+  val tests = Tests {
+    test("shouldSetTwoKnifes") {
+      val i = Inventory(Set(), Set(Knife("Knife")), Set(Knife("Knife")))
+      println(i.allEquipment)
+      assert(i.allEquipment.size == 2)
+    }
+  }
+}