diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/.formatter.exs b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/.formatter.exs
new file mode 100644
index 0000000..d2cda26
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/.formatter.exs
@@ -0,0 +1,4 @@
+# Used by "mix format"
+[
+  inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
+]
diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/.gitignore b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/.gitignore
new file mode 100644
index 0000000..98f70cd
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/.gitignore
@@ -0,0 +1,24 @@
+# The directory Mix will write compiled artifacts to.
+/_build/
+
+# If you run "mix test --cover", coverage assets end up here.
+/cover/
+
+# The directory Mix downloads your dependencies sources to.
+/deps/
+
+# Where third-party dependencies like ExDoc output generated docs.
+/doc/
+
+# Ignore .fetch files in case you like to edit your project deps locally.
+/.fetch
+
+# If the VM crashes, it generates a dump, let's ignore it too.
+erl_crash.dump
+
+# Also ignore archive artifacts (built via "mix archive.build").
+*.ez
+
+# Ignore package tarball (built via "mix hex.build").
+cart-*.tar
+
diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/README.md b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/README.md
new file mode 100644
index 0000000..7c8ab3a
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/README.md
@@ -0,0 +1,21 @@
+# Cart
+
+**TODO: Add description**
+
+## Installation
+
+If [available in Hex](https://hex.pm/docs/publish), the package can be installed
+by adding `cart` to your list of dependencies in `mix.exs`:
+
+```elixir
+def deps do
+  [
+    {:cart, "~> 0.1.0"}
+  ]
+end
+```
+
+Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
+and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
+be found at [https://hexdocs.pm/cart](https://hexdocs.pm/cart).
+
diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/lib/cart.ex b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/lib/cart.ex
new file mode 100644
index 0000000..a699b0f
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/lib/cart.ex
@@ -0,0 +1,57 @@
+defmodule Cart do
+  @moduledoc """
+  Documentation for Cart.
+  """
+
+  def show_cart(events) when is_list(events) do
+    Enum.reverse(events)
+    |> Enum.reduce(
+      [],
+      fn {event, {product, qty, price}}, cart ->
+        adjustment = calculate_adjustment(event, qty)
+        [{_product, {qty, _price}} | rest] = move_to_head(cart, product)
+
+        [{product, {qty + adjustment, price}} | rest]
+        |> remove_item_with_zero_qty()
+      end
+    )
+  end
+
+  def calculate_adjustment(:item_added, qty) do
+    qty
+  end
+
+  def calculate_adjustment(:item_removed, qty) do
+    -1 * qty
+  end
+
+  def move_to_head(cart, product) do
+    item_to_move = Enum.find(cart, {product, {0, 0.00}}, fn {item, _} -> item == product end)
+    rest_of_items = Enum.filter(cart, fn {item, _} -> item != product end)
+    [item_to_move | rest_of_items]
+  end
+
+  def remove_item_with_zero_qty(cart) do
+    Enum.filter(cart, fn {_product, {qty, _price}} -> qty > 0 end)
+  end
+
+  def get_total(events) do
+    show_cart(events) |> Enum.reduce(0, fn {_product, {qty, price}}, sum -> sum + qty * price end)
+  end
+
+  def get_count(events) do
+    show_cart(events) |> Enum.reduce(0, fn {_product, {qty, _price}}, sum -> sum + qty end)
+  end
+
+  def get_added_items(events) do
+    events
+    |> Enum.filter(fn {event_type, _} -> event_type == :item_added end)
+    |> Enum.reduce([], fn {_event, {product, _, _}}, products -> [product | products] end)
+  end
+
+  def get_removed_items(events) do
+    events
+    |> Enum.filter(fn {event_type, _} -> event_type == :item_removed end)
+    |> Enum.reduce([], fn {_event, {product, _, _}}, products -> [product | products] end)
+  end
+end
diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/mix.exs b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/mix.exs
new file mode 100644
index 0000000..1c7b315
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/mix.exs
@@ -0,0 +1,28 @@
+defmodule Cart.MixProject do
+  use Mix.Project
+
+  def project do
+    [
+      app: :cart,
+      version: "0.1.0",
+      elixir: "~> 1.10",
+      start_permanent: Mix.env() == :prod,
+      deps: deps()
+    ]
+  end
+
+  # Run "mix help compile.app" to learn about applications.
+  def application do
+    [
+      extra_applications: [:logger]
+    ]
+  end
+
+  # Run "mix help deps" to learn about dependencies.
+  defp deps do
+    [
+      # {:dep_from_hexpm, "~> 0.3.0"},
+      # {:dep_from_git, git: "https://github.com/elixir-lang/my_dep.git", tag: "0.1.0"}
+    ]
+  end
+end
diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/test/cart_test.exs b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/test/cart_test.exs
new file mode 100644
index 0000000..176ac11
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/test/cart_test.exs
@@ -0,0 +1,123 @@
+defmodule CartTest do
+  use ExUnit.Case
+
+  test "show_cart(events) returns an empty list for an empty cart" do
+    events = []
+    assert Cart.show_cart(events) == []
+  end
+
+  test "show_card(events) returns an empty list for a cart that has item added and then removed" do
+    random_qty = Enum.random(1..100)
+
+    events = [
+      {:item_removed, {:dinosaur_egg, random_qty, 125.00}},
+      {:item_added, {:dinosaur_egg, random_qty, 125.00}}
+    ]
+
+    assert Cart.show_cart(events) == []
+  end
+
+  test "show_cart(events) returns a list of current items in the right form" do
+    items = [
+      {:iguana_leash, {4, 12.00}},
+      {:zombie_repelent, {12, 3.00}}
+    ]
+
+    events = [
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_removed, {:iguana_leash, 1, 12.00}},
+      {:item_added, {:iguana_leash, 2, 12.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}}
+    ]
+
+    assert Cart.show_cart(events) == items
+  end
+
+  test "get_total(events) returns a zero for an empty cart" do
+    events = []
+    assert Cart.get_total(events) == 0.00
+  end
+
+  test "get_total(events) returns a floating point number for the total cost of all products in the cart" do
+    events = [
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}}
+    ]
+
+    assert Cart.get_total(events) == 72.00
+  end
+
+  test "get_count(events) returns a zero for an empty cart" do
+    events = []
+    assert Cart.get_count(events) == 0
+  end
+
+  test "get_count(events) returns a number of items in a cart" do
+    events = [
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}}
+    ]
+
+    assert Cart.get_count(events) == 15
+  end
+
+  test "get_added_items(events) returns an empty list for an empty cart" do
+    events = []
+    assert Cart.get_added_items(events) == []
+  end
+
+  test "get_added_items(events) returns an empty list for a cart with only removed items" do
+    events = [
+      {:item_removed, {:iguana_leash, 3, 12.00}},
+      {:item_removed, {:zombie_repelent, 12, 3.00}}
+    ]
+
+    assert Cart.get_added_items(events) == []
+  end
+
+  test "get_added_items(events) returns a list of added items for a cart" do
+    events = [
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_removed, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}},
+      {:item_removed, {:zombie_repelent, 5, 3.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}},
+      {:item_added, {:iguana_leash, 3, 12.00}}
+    ]
+
+    items = [:iguana_leash, :zombie_repelent, :zombie_repelent, :iguana_leash, :iguana_leash]
+
+    assert Cart.get_added_items(events) == items
+  end
+
+  test "get_removed_items(events) returns an empty list for an empty cart" do
+    events = []
+    assert Cart.get_removed_items(events) == []
+  end
+
+  test "get_removed_items(events) returns an empty list for a cart with only added items" do
+    events = [
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}}
+    ]
+
+    assert Cart.get_removed_items(events) == []
+  end
+
+  test "get_removed_items(events) returns a list of items removed form a cart" do
+    events = [
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_removed, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:iguana_leash, 3, 12.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}},
+      {:item_removed, {:zombie_repelent, 5, 3.00}},
+      {:item_added, {:zombie_repelent, 12, 3.00}},
+      {:item_added, {:iguana_leash, 3, 12.00}}
+    ]
+
+    items = [:zombie_repelent, :iguana_leash]
+
+    assert Cart.get_removed_items(events) == items
+  end
+end
diff --git a/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/test/test_helper.exs b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/test/test_helper.exs
new file mode 100644
index 0000000..869559e
--- /dev/null
+++ b/workshops/an_ounce_of_elixir_2020/cart_krakow_12_feb_2020/test/test_helper.exs
@@ -0,0 +1 @@
+ExUnit.start()