diff --git a/lib/xebow/engine.ex b/lib/xebow/engine.ex
index bc54dcf..464b62b 100644
--- a/lib/xebow/engine.ex
+++ b/lib/xebow/engine.ex
@@ -6,8 +6,6 @@ defmodule Xebow.Engine do
 
   use GenServer
 
-  import Xebow.Utils, only: [mod: 2]
-
   alias Xebow.Animation
 
   defmodule State do
@@ -35,22 +33,6 @@ defmodule Xebow.Engine do
     GenServer.start_link(__MODULE__, {initial_animation, paintables}, name: __MODULE__)
   end
 
-  @doc """
-  Cycle to the next animation and play it.
-  """
-  @spec next_animation :: :ok
-  def next_animation do
-    GenServer.cast(__MODULE__, :next_animation)
-  end
-
-  @doc """
-  Cycle to the previous animation and play it.
-  """
-  @spec previous_animation :: :ok
-  def previous_animation do
-    GenServer.cast(__MODULE__, :previous_animation)
-  end
-
   @doc """
   Play the given animation.
 
@@ -145,31 +127,8 @@ defmodule Xebow.Engine do
   end
 
   @impl GenServer
-  def handle_cast(:next_animation, state) do
-    animation_types = Animation.types()
-    num = Enum.count(animation_types)
-    current = Enum.find_index(animation_types, &(&1 == state.animation.type))
-    next = mod(current + 1, num)
-    animation_type = Enum.at(animation_types, next)
-    animation = Animation.new(type: animation_type)
-
-    {:noreply, set_animation(state, animation)}
-  end
-
-  @impl GenServer
-  def handle_cast(:previous_animation, state) do
-    animation_types = Animation.types()
-    num = Enum.count(animation_types)
-    current = Enum.find_index(animation_types, &(&1 == state.animation.type))
-    previous = mod(current - 1, num)
-    animation_type = Enum.at(animation_types, previous)
-    animation = Animation.new(type: animation_type)
-
-    {:noreply, set_animation(state, animation)}
-  end
-
-  @impl GenServer
-  def handle_cast({:play_animation, %{loop: loop} = animation}, state) when loop >= 1 do
+  def handle_cast({:play_animation, %{loop: loop} = animation}, state)
+      when is_integer(loop) and loop >= 1 do
     current_animation = state.animation
     expected_duration = Animation.duration(animation)
     Process.send_after(self(), {:reset_animation, current_animation}, expected_duration)
@@ -188,7 +147,8 @@ defmodule Xebow.Engine do
   end
 
   @impl GenServer
-  def handle_call({:play_animation, %{loop: loop} = animation}, from, state) when loop >= 1 do
+  def handle_call({:play_animation, %{loop: loop} = animation}, from, state)
+      when is_integer(loop) and loop >= 1 do
     current_animation = state.animation
     duration = Animation.duration(animation)
     Process.send_after(self(), {:reply, from, current_animation}, duration)
diff --git a/lib/xebow/keys.ex b/lib/xebow/keys.ex
index c1fcf08..01ac1be 100644
--- a/lib/xebow/keys.ex
+++ b/lib/xebow/keys.ex
@@ -73,8 +73,25 @@ defmodule Xebow.Keys do
 
   # Client
 
-  def start_link([], opts \\ []) do
-    GenServer.start_link(__MODULE__, [], opts)
+  @spec start_link(any()) :: GenServer.on_start()
+  def start_link(_) do
+    GenServer.start_link(__MODULE__, [], name: __MODULE__)
+  end
+
+  @doc """
+  Cycle to the next animation
+  """
+  @spec next_animation() :: :ok
+  def next_animation do
+    GenServer.cast(__MODULE__, :next_animation)
+  end
+
+  @doc """
+  Cycle to the previous animation
+  """
+  @spec previous_animation() :: :ok
+  def previous_animation do
+    GenServer.cast(__MODULE__, :previous_animation)
   end
 
   # Server
@@ -102,20 +119,65 @@ defmodule Xebow.Keys do
     poll_timer_ms = 15
     :timer.send_interval(poll_timer_ms, self(), :update_pin_values)
 
+    animations =
+      Animation.types()
+      |> Enum.map(&Animation.new(type: &1))
+
     {:ok,
      %{
        pins: pins,
        keyboard_state: keyboard_state,
-       hid: hid
+       hid: hid,
+       animations: animations,
+       current_animation_index: 0
      }}
   end
 
+  @impl GenServer
+  def handle_cast(:next_animation, state) do
+    next_index = state.current_animation_index + 1
+
+    next_index =
+      case next_index < Enum.count(state.animations) do
+        true -> next_index
+        _ -> 0
+      end
+
+    animation = Enum.at(state.animations, next_index)
+
+    Xebow.Engine.play_animation(animation)
+
+    state = %{state | current_animation_index: next_index}
+
+    {:noreply, state}
+  end
+
+  @impl GenServer
+  def handle_cast(:previous_animation, state) do
+    previous_index = state.current_animation_index - 1
+
+    previous_index =
+      case previous_index < 0 do
+        true -> Enum.count(state.animations) - 1
+        _ -> previous_index
+      end
+
+    animation = Enum.at(state.animations, previous_index)
+
+    Xebow.Engine.play_animation(animation)
+
+    state = %{state | current_animation_index: previous_index}
+
+    {:noreply, state}
+  end
+
   @impl GenServer
   def handle_info({:hid_report, hid_report}, state) do
     IO.binwrite(state.hid, hid_report)
     {:noreply, state}
   end
 
+  @impl GenServer
   def handle_info(:update_pin_values, state) do
     new_pins =
       Enum.map(state.pins, fn {pin_number, pin_ref, old_value} ->
@@ -158,14 +220,6 @@ defmodule Xebow.Keys do
     Xebow.Engine.play_animation(animation, async: false)
   end
 
-  def next_animation do
-    Xebow.Engine.next_animation()
-  end
-
-  def previous_animation do
-    Xebow.Engine.previous_animation()
-  end
-
   def start_wifi_wizard do
     case VintageNetWizard.run_wizard() do
       :ok -> flash("green")