diff --git a/config/config.exs b/config/config.exs
index 3157f5c..bd204f6 100644
--- a/config/config.exs
+++ b/config/config.exs
@@ -68,6 +68,8 @@ config :viral_spiral, RoomConfig,
   chaos_counter: 10,
   volatility: :medium
 
+config :viral_spiral, CardConfig, card_types: [:affinity, :bias, :topical, :conflated]
+
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{config_env()}.exs"
diff --git a/lib/viral_spiral/deck/card.ex b/lib/viral_spiral/deck/card.ex
new file mode 100644
index 0000000..8efef0b
--- /dev/null
+++ b/lib/viral_spiral/deck/card.ex
@@ -0,0 +1,21 @@
+defmodule ViralSpiral.Deck.Card do
+  import ViralSpiral.Deck.CardGuards
+  alias ViralSpiral.Deck.Card
+
+  defstruct id: nil,
+            type: nil
+
+  @type card_types :: :affinity | :bias | :topical | :conflated
+
+  @type t :: %__MODULE__{
+          id: String.t(),
+          type: card_types()
+        }
+
+  def new(type) when is_card_type(type) do
+    %Card{
+      id: UXID.generate!(prefix: "card", size: :small),
+      type: type
+    }
+  end
+end
diff --git a/lib/viral_spiral/deck/card_content.ex b/lib/viral_spiral/deck/card_content.ex
new file mode 100644
index 0000000..abb5d4c
--- /dev/null
+++ b/lib/viral_spiral/deck/card_content.ex
@@ -0,0 +1,6 @@
+defmodule ViralSpiral.Deck.CardContent do
+  defstruct title: "",
+            description: "",
+            fake_title: "",
+            fake_description: ""
+end
diff --git a/lib/viral_spiral/deck/card_guards.ex b/lib/viral_spiral/deck/card_guards.ex
new file mode 100644
index 0000000..fad74e2
--- /dev/null
+++ b/lib/viral_spiral/deck/card_guards.ex
@@ -0,0 +1,5 @@
+defmodule ViralSpiral.Deck.CardGuards do
+  @card_types Application.compile_env(:viral_spiral, CardConfig)[:card_types]
+
+  defguard is_card_type(value) when value in @card_types
+end
diff --git a/lib/viral_spiral/game.ex b/lib/viral_spiral/game.ex
index 1808377..d7bc17d 100644
--- a/lib/viral_spiral/game.ex
+++ b/lib/viral_spiral/game.ex
@@ -1,4 +1,11 @@
 defmodule ViralSpiral.Game do
+  @moduledoc """
+  Context for Game
+  """
+  alias ViralSpiral.Game.State
+  alias ViralSpiral.Game.Score.Player
+  alias ViralSpiral.Game.Player
+  alias ViralSpiral.Deck.Card
   alias ViralSpiral.Game.Room
 
   @spec create_room(String.t()) :: Room.t()
@@ -9,7 +16,17 @@ defmodule ViralSpiral.Game do
   def join_room(_name, _password) do
   end
 
-  def pass_card(_state, _player, _to) do
+  @doc """
+  Pass a card from one player to another.
+  """
+  # @spec pass_card(Player.t(), Card.t()) :: list(Change.t())
+  def pass_card(state, %Card{} = card, %Player{} = from, %Player{} = _to) do
+    changes =
+      case card.type do
+        :affinity -> [{state.player_scores[from.id], [type: :inc, target: :affinity, count: 1]}]
+      end
+
+    State.apply_changes(state, changes)
   end
 
   def keep_card(_player) do
@@ -24,6 +41,9 @@ defmodule ViralSpiral.Game do
   def cancel_player(_player, _target) do
   end
 
+  def cancel_player_vote(_player, _target) do
+  end
+
   def viral_spiral(_player, _targets) do
   end
 end
diff --git a/lib/viral_spiral/game/_change.ex b/lib/viral_spiral/game/_change.ex
new file mode 100644
index 0000000..9c0d021
--- /dev/null
+++ b/lib/viral_spiral/game/_change.ex
@@ -0,0 +1,14 @@
+# defmodule ViralSpiral.Game.Change do
+#   defstruct type: nil,
+#             target: nil,
+#             target_id: nil
+
+#   @type change_type :: :inc | :dec | :value
+#   @type target :: :chaos_counter | :clout | :affinity | :bias
+
+#   @type t :: %__MODULE__{
+#           type: change_type(),
+#           target: target(),
+#           target_id: String.t()
+#         }
+# end
diff --git a/lib/viral_spiral/game/player.ex b/lib/viral_spiral/game/player.ex
index 8195e9a..43d30c9 100644
--- a/lib/viral_spiral/game/player.ex
+++ b/lib/viral_spiral/game/player.ex
@@ -1,4 +1,5 @@
 defmodule ViralSpiral.Game.Player do
+  alias ViralSpiral.Deck.Card
   alias ViralSpiral.Game.Player
   alias ViralSpiral.Game.RoomConfig
 
@@ -7,6 +8,13 @@ defmodule ViralSpiral.Game.Player do
             identity: nil,
             hand: []
 
+  @type t :: %__MODULE__{
+          id: String.t(),
+          name: String.t(),
+          identity: atom(),
+          hand: list(Card.t())
+        }
+
   def new() do
     %Player{
       id: UXID.generate!(prefix: "player", size: :small)
diff --git a/lib/viral_spiral/game/score.ex b/lib/viral_spiral/game/score.ex
deleted file mode 100644
index e3a6f02..0000000
--- a/lib/viral_spiral/game/score.ex
+++ /dev/null
@@ -1,51 +0,0 @@
-defmodule ViralSpiral.Game.Score.Room do
-  alias ViralSpiral.Game.Score.Room
-  defstruct chaos_countdown: 10
-
-  def new() do
-    %Room{}
-  end
-
-  def countdown(%Room{} = room) do
-    %{room | chaos_countdown: room.chaos_countdown - 1}
-  end
-end
-
-defmodule ViralSpiral.Game.Score.Player do
-  alias ViralSpiral.Game.Score.Player
-  alias ViralSpiral.Game.RoomConfig
-  alias ViralSpiral.Game.Player, as: PlayerData
-  import ViralSpiral.Game.RoomConfig.Guards
-
-  defstruct biases: %{}, affinities: %{}, clout: 0
-
-  def new(%PlayerData{} = player, %RoomConfig{} = room_config) do
-    bias_list = Enum.filter(room_config.communities, &(&1 != player.identity))
-    bias_map = Enum.reduce(bias_list, %{}, fn x, acc -> Map.put(acc, x, 0) end)
-
-    affinity_list = room_config.affinities
-    affinity_map = Enum.reduce(affinity_list, %{}, fn x, acc -> Map.put(acc, x, 0) end)
-
-    %Player{
-      biases: bias_map,
-      affinities: affinity_map
-    }
-  end
-
-  def change(%Player{} = player, :bias, target_bias, count)
-      when is_community(target_bias) and is_integer(count) do
-    new_biases = Map.put(player.biases, target_bias, player.biases[target_bias] + count)
-    %{player | biases: new_biases}
-  end
-
-  def change(%Player{} = player, :affinity, target, count)
-      when is_affinity(target) and is_integer(count) do
-    new_affinities = Map.put(player.affinities, target, player.affinities[target] + count)
-    %{player | affinities: new_affinities}
-  end
-
-  def change(%Player{} = player, :clout, count) when is_integer(count) do
-    new_clout = player.clout + count
-    %{player | clout: new_clout}
-  end
-end
diff --git a/lib/viral_spiral/game/state.ex b/lib/viral_spiral/game/state.ex
index f6e016a..9075391 100644
--- a/lib/viral_spiral/game/state.ex
+++ b/lib/viral_spiral/game/state.ex
@@ -18,6 +18,7 @@ defmodule ViralSpiral.Game.State do
   When a round begins, we also start a Turn. Within each Round there's a turn that includes everyone except the person who started the turn.
   """
   alias ViralSpiral.Game.State
+  alias ViralSpiral.Game.Change
 
   def set_round(%State{} = game, round) do
     %State{game | round: round}
@@ -26,4 +27,28 @@ defmodule ViralSpiral.Game.State do
   def set_turn(%State{} = game, turn) do
     %State{game | turn: turn}
   end
+
+  # @spec apply_changes(list(Change.t())) ::
+  #         list({:ok, message :: String.t()} | {:error, reason :: String.t()})
+  def apply_changes(state, changes) do
+    # Enum.reduce(changes, [], &(&2 ++ [apply_change(elem(&1, 0), elem(&1, 1))]))
+    _results = Enum.map(changes, &apply(elem(&1, 0), elem(&1, 1)))
+    # new_state = Enum.reduce(results, state, &)
+
+    # results = Enum.reduce...
+    # state = Enum.reduce(results, state, &Map.put(&1.id, &1.value))
+  end
+
+  defdelegate apply_change(change, opts), to: Change
+
+  # @doc """
+  # Change various components of state.
+
+  # round, turn, room, card, player_score
+  # """
+  # def apply(state, change) do
+  #   case change do
+  #     %{id: id, value: value}
+  #   end
+  # end
 end
diff --git a/lib/viral_spiral/game/turn.ex b/lib/viral_spiral/game/turn.ex
index 6586a49..b4e14f6 100644
--- a/lib/viral_spiral/game/turn.ex
+++ b/lib/viral_spiral/game/turn.ex
@@ -14,7 +14,7 @@ defmodule ViralSpiral.Game.Turn do
             pass_to: []
 
   @type t :: %__MODULE__{
-          current: String.t(),
+          current: String.t() | nil,
           pass_to: list(String.t())
         }
 
diff --git a/lib/viral_spiral/score/change.ex b/lib/viral_spiral/score/change.ex
new file mode 100644
index 0000000..4184fe9
--- /dev/null
+++ b/lib/viral_spiral/score/change.ex
@@ -0,0 +1,10 @@
+defprotocol ViralSpiral.Score.Change do
+  @moduledoc """
+  Protocol to change scores used in Viral Spiral.
+
+  ## Fields
+  - score: struct which implements the `Change` protocol
+  - change_description: a Keyword List with parameters defining the change
+  """
+  def apply_change(score, change_description)
+end
diff --git a/lib/viral_spiral/score/player.ex b/lib/viral_spiral/score/player.ex
new file mode 100644
index 0000000..2b28c37
--- /dev/null
+++ b/lib/viral_spiral/score/player.ex
@@ -0,0 +1,70 @@
+defmodule ViralSpiral.Score.Player do
+  @moduledoc """
+  Create and update Player Score.
+
+  ## Example
+  iex> player_score = %ViralSpiral.Game.Score.Player{
+      biases: %{red: 0, blue: 0},
+      affinities: %{cat: 0, sock: 0},
+      clout: 0
+    }
+  """
+  alias ViralSpiral.Score.Player
+  alias ViralSpiral.Game.RoomConfig
+  alias ViralSpiral.Game.Player, as: PlayerData
+  import ViralSpiral.Game.RoomConfig.Guards
+  alias ViralSpiral.Score.Change
+
+  defstruct biases: %{}, affinities: %{}, clout: 0
+
+  @type change_opts :: [type: :clout | :affinity | :bias, offset: integer(), target: atom()]
+  @type t :: %__MODULE__{
+          biases: map(),
+          affinities: map(),
+          clout: integer()
+        }
+
+  def new(%PlayerData{} = player, %RoomConfig{} = room_config) do
+    bias_list = Enum.filter(room_config.communities, &(&1 != player.identity))
+    bias_map = Enum.reduce(bias_list, %{}, fn x, acc -> Map.put(acc, x, 0) end)
+
+    affinity_list = room_config.affinities
+    affinity_map = Enum.reduce(affinity_list, %{}, fn x, acc -> Map.put(acc, x, 0) end)
+
+    %Player{
+      biases: bias_map,
+      affinities: affinity_map
+    }
+  end
+
+  defimpl Change do
+    @doc """
+    Implement change protocol for a Player's Score.
+    """
+    @spec apply_change(Player.t(), Player.change_opts()) :: Player.t()
+    def apply_change(player, opts) do
+      case opts[:type] do
+        :clout -> change(player, :clout, opts[:offset])
+        :affinity -> change(player, :affinity, opts[:target], opts[:offset])
+        :bias -> change(player, :bias, opts[:target], opts[:offset])
+      end
+    end
+
+    def change(%Player{} = player, :bias, target_bias, count)
+        when is_community(target_bias) and is_integer(count) do
+      new_biases = Map.put(player.biases, target_bias, player.biases[target_bias] + count)
+      %{player | biases: new_biases}
+    end
+
+    def change(%Player{} = player, :affinity, target, count)
+        when is_affinity(target) and is_integer(count) do
+      new_affinities = Map.put(player.affinities, target, player.affinities[target] + count)
+      %{player | affinities: new_affinities}
+    end
+
+    def change(%Player{} = player, :clout, count) when is_integer(count) do
+      new_clout = player.clout + count
+      %{player | clout: new_clout}
+    end
+  end
+end
diff --git a/lib/viral_spiral/score/room.ex b/lib/viral_spiral/score/room.ex
new file mode 100644
index 0000000..d1234e1
--- /dev/null
+++ b/lib/viral_spiral/score/room.ex
@@ -0,0 +1,38 @@
+defmodule ViralSpiral.Score.Room do
+  @moduledoc """
+  ## Example
+
+  """
+  alias ViralSpiral.Score.Change
+  alias ViralSpiral.Score.Room
+  defstruct chaos_countdown: 10
+
+  @type t :: %__MODULE__{
+          chaos_countdown: integer()
+        }
+
+  @spec new() :: ViralSpiral.Score.Room.t()
+  def new() do
+    %Room{}
+  end
+
+  @spec countdown(ViralSpiral.Score.Room.t()) :: ViralSpiral.Score.Room.t()
+  def countdown(%Room{} = room) do
+    %{room | chaos_countdown: room.chaos_countdown - 1}
+  end
+
+  defimpl Change do
+    @spec apply_change(ViralSpiral.Score.Room.t(), keyword()) :: ViralSpiral.Score.Room.t()
+    def apply_change(%Room{} = score, opts) do
+      opts = Keyword.validate!(opts, offset: 0)
+
+      case opts[:offset] do
+        x when is_integer(x) ->
+          Map.put(score, :chaos_countdown, score.chaos_countdown + opts[:offset])
+
+        y when is_bitstring(y) ->
+          Map.put(score, :chaos_countdown, score.chaos_countdown)
+      end
+    end
+  end
+end
diff --git a/test/support/fixtures.ex b/test/support/fixtures.ex
index 90f2988..852ac1c 100644
--- a/test/support/fixtures.ex
+++ b/test/support/fixtures.ex
@@ -1,4 +1,5 @@
 defmodule Fixtures do
+  alias ViralSpiral.Deck.Card
   alias ViralSpiral.Game.Score.Player
   alias ViralSpiral.Game.Turn
   alias ViralSpiral.Game.Round
@@ -10,7 +11,7 @@ defmodule Fixtures do
   alias ViralSpiral.Game.State
 
   def initialized_game() do
-    room_config = %RoomConfig{} |> IO.inspect()
+    room_config = %RoomConfig{}
 
     player_list = [
       Player.new(room_config) |> Player.set_name("adhiraj"),
@@ -24,6 +25,17 @@ defmodule Fixtures do
     round = Round.new(player_list)
     turn = Turn.new(round)
 
+    player_score_list =
+      Enum.map(
+        player_list,
+        &(Map.new() |> Map.put(:id, &1.id) |> Map.put(:score, PlayerScore.new(&1, room_config)))
+      )
+
+    player_score_map =
+      Enum.reduce(player_score_list, %{}, fn player, acc ->
+        Map.put(acc, player.id, player.score)
+      end)
+
     %State{
       room_config: room_config,
       room: Room.new(),
@@ -32,7 +44,11 @@ defmodule Fixtures do
       round: round,
       turn: turn,
       # room_score: RoomScore.new(),
-      player_scores: Enum.map(player_list, &PlayerScore.new(&1, room_config))
+      player_scores: player_score_map
     }
   end
+
+  def card_affinity() do
+    Card.new(:affinity)
+  end
 end
diff --git a/test/viral_spiral/gameplay_test.exs b/test/viral_spiral/gameplay_test.exs
index 8b989cb..7aad115 100644
--- a/test/viral_spiral/gameplay_test.exs
+++ b/test/viral_spiral/gameplay_test.exs
@@ -1,4 +1,5 @@
 defmodule ViralSpiral.GameTest do
+  alias ViralSpiral.Game
   use ExUnit.Case
 
   describe "card actions" do
@@ -7,12 +8,22 @@ defmodule ViralSpiral.GameTest do
       %{state: game_state}
     end
 
-    test "passing an affinity card", %{state: game_state} do
+    test "passing an affinity card changes the player's clout and affinity", %{state: game_state} do
       players = game_state.player_map
       round = game_state.round
       turn = game_state.turn
       room_score = game_state.room_score
       player_scores = game_state.player_scores
+
+      card = Fixtures.card_affinity()
+
+      current_player = players[turn.current]
+      target_player = players[2]
+
+      Game.pass_card(game_state, card, current_player, target_player)
+
+      IO.inspect(game_state)
+      # IO.inspect(card)
     end
   end
 end
diff --git a/test/viral_spiral/score/player_text.exs b/test/viral_spiral/score/player_text.exs
new file mode 100644
index 0000000..a651e58
--- /dev/null
+++ b/test/viral_spiral/score/player_text.exs
@@ -0,0 +1,30 @@
+defmodule ViralSpiral.Score.PlayerTest do
+  alias ViralSpiral.Score.Change
+  alias ViralSpiral.Score.Player
+  use ExUnit.Case
+
+  setup_all do
+    player = %Player{
+      biases: %{red: 0, blue: 0},
+      affinities: %{cat: 0, sock: 0},
+      clout: 0
+    }
+
+    %{player: player}
+  end
+
+  test "change player clout", %{player: player} do
+    new_player = Change.apply_change(player, type: :clout, offset: 5)
+    assert new_player.clout == 5
+  end
+
+  test "change player affinity", %{player: player} do
+    new_player = Change.apply_change(player, type: :affinity, target: :cat, offset: -2)
+    assert new_player.affinities.cat == -2
+  end
+
+  test "change player bias", %{player: player} do
+    new_player = Change.apply_change(player, type: :bias, target: :red, offset: 9)
+    assert new_player.biases.red == 9
+  end
+end
diff --git a/test/viral_spiral/score/room_test.exs b/test/viral_spiral/score/room_test.exs
new file mode 100644
index 0000000..4030005
--- /dev/null
+++ b/test/viral_spiral/score/room_test.exs
@@ -0,0 +1,33 @@
+defmodule ViralSpiral.Score.RoomTest do
+  alias ViralSpiral.Score.Change
+  alias ViralSpiral.Score.Room
+  use ExUnit.Case
+
+  setup_all do
+    room = %Room{chaos_countdown: 4}
+    %{room: room}
+  end
+
+  test "change chaos countdown", %{room: room} do
+    new_room = Change.apply_change(room, offset: 5)
+    assert new_room.chaos_countdown == 9
+  end
+
+  describe "invalid changes" do
+    setup do
+      room = %Room{chaos_countdown: 2}
+      %{room: room}
+    end
+
+    test "pass invalid offset in change description", %{room: room} do
+      new_room = Change.apply_change(room, offset: "hi")
+      assert new_room.chaos_countdown == 2
+    end
+
+    test "pass opts without required fields", %{room: room} do
+      assert_raise ArgumentError, fn ->
+        Change.apply_change(room, invalid: "random")
+      end
+    end
+  end
+end