diff --git a/2015-elixir/README.md b/2015-elixir/README.md
index e0b58fa..b535d32 100644
--- a/2015-elixir/README.md
+++ b/2015-elixir/README.md
@@ -1,8 +1,8 @@
 # Aoc
 
-Solutions for [Advent of Code 2020][1], this year in Elixir.
+Solutions for [Advent of Code 2021][1], this year in Elixir.
 
-[Elixir 1.11.1][2] preferred.
+[Elixir 1.12.3][2] preferred.
 
 ## Help scripts
 
diff --git a/2015-elixir/lib/aoc.ex b/2015-elixir/lib/aoc.ex
index f20e7a6..56160eb 100644
--- a/2015-elixir/lib/aoc.ex
+++ b/2015-elixir/lib/aoc.ex
@@ -1,12 +1,9 @@
 defmodule Aoc do
-  @moduledoc """
-  Solutions for Advent of Code 2020, written in Elixir 1.11.1.
-  """
-
+  @year 2021
   def solve_all() do
     """
 
-    ADVENT OF CODE 2020
+    ADVENT OF CODE #{@year}
     ===================
     """
     |> IO.puts()
diff --git a/2015-elixir/lib/mix/tasks/bootstrap.ex b/2015-elixir/lib/mix/tasks/bootstrap.ex
index 45a061b..e0ff897 100644
--- a/2015-elixir/lib/mix/tasks/bootstrap.ex
+++ b/2015-elixir/lib/mix/tasks/bootstrap.ex
@@ -3,6 +3,9 @@ defmodule Mix.Tasks.Aoc.New do
 
   @shortdoc "Bootstrap new solution"
   @impl Mix.Task
+
+  @year 2021
+
   def run([n, name]) do
     id = n |> String.pad_leading(2, "0")
 
@@ -17,17 +20,17 @@ defmodule Mix.Tasks.Aoc.New do
     File.write!(test_file, test_file_content(id))
 
     IO.puts("Creating " <> solution_file)
-    File.write!(solution_file, solution_file_content(name, id))
+    File.write!(solution_file, solution_file_content(name, id, n))
 
     """
     \nDone! Start coding.
 
     Get your puzzle input here:
-    https://adventofcode.com/2015/day/#{id}/input
+    https://adventofcode.com/#{@year}/day/#{n}/input
 
     mix test                 -- run tests.
-    mix Aoc.solve_all        -- run all puzzles, starting with 1
-    mix Aoc.solve #{id}         -- run single puzzle, 1-25
+    mix aoc.solve_all        -- run all puzzles, starting with 1
+    mix aoc.solve #{id}         -- run single puzzle, 1-25
     """
     |> IO.puts()
   end
@@ -48,22 +51,22 @@ defmodule Mix.Tasks.Aoc.New do
       test "solves first part" do
         a = "something" |> parse!() |> solve_first_part()
 
-        expect a == :something
+        assert a == :something
       end
 
       test "solves second part" do
         a = "something" |> parse!() |> solve_second_part()
 
-        expect a == :something
+        assert a == :something
       end
     end
     """
   end
 
-  defp solution_file_content(name, id) do
+  defp solution_file_content(name, id, n) do
     ~s"""
     defmodule Aoc.Solution.Day#{id} do
-      @name "#{name}"
+      @name "Day #{n}: #{name}"
       @behaviour Solution
 
       @impl Solution
diff --git a/2015-elixir/lib/solutions/day_06.ex b/2015-elixir/lib/solutions/day_06.ex
new file mode 100644
index 0000000..a6a226b
--- /dev/null
+++ b/2015-elixir/lib/solutions/day_06.ex
@@ -0,0 +1,96 @@
+defmodule Aoc.Solution.Day06 do
+  @name "Day 6: Probably a Fire Hazard"
+  @behaviour Solution
+
+  @impl Solution
+  def get_name, do: @name
+
+  @impl Solution
+  def parse!(raw) do
+    r = ~r/ ?(\S+) (\d+),(\d+) through (\d+),(\d+)/
+
+    raw
+    |> String.split("\n")
+    |> Enum.map(fn row ->
+      [_, verb, x1, y1, x2, y2] = Regex.run(r, row)
+      {verb, String.to_integer(x1)..String.to_integer(x2), String.to_integer(y1)..String.to_integer(y2)}
+    end)
+  end
+
+  @impl Solution
+  def solve_first_part(input) do
+    lit = MapSet.new()
+    change_state(lit, input) |> MapSet.size()
+  end
+
+  @impl Solution
+  def solve_second_part(input) do
+    lit = Map.new()
+    adjust_brightness(lit, input)
+  end
+
+  defp change_state(lit, []) do
+    lit
+  end
+
+  defp change_state(lit, [ {verb, xset, yset} | remaining]) do
+    change = for x <- xset do
+      for y <- yset do
+        {x, y}
+      end
+    end |> List.flatten() |> MapSet.new()
+    case verb do
+      "on" ->
+        change_state(MapSet.union(lit, change), remaining)
+
+      "off" ->
+        change_state(MapSet.difference(lit, change), remaining)
+
+      "toggle" ->
+        to_lit = MapSet.difference(change, lit)
+        to_unlit = MapSet.difference(lit, change)
+        change_state(MapSet.union(to_lit, to_unlit), remaining)
+    end
+  end
+
+  defp adjust_brightness(lit, []) do
+    Map.values(lit) |> Enum.sum
+  end
+
+  defp adjust_brightness(lit, [ {verb, xset, yset} | remaining]) do
+    change = for x <- xset do
+      for y <- yset do
+        {x, y}
+      end
+    end |> List.flatten()
+    updated = case verb do
+      "on" ->
+        Enum.reduce(change, lit, fn xy, acc ->
+          if Map.has_key?(acc, xy) do
+            %{acc | xy => Map.get(acc, xy) + 1}
+          else
+            Map.put(acc, xy, 1)
+          end
+        end)
+
+      "off" ->
+        Enum.reduce(change, lit, fn xy, acc ->
+          if Map.has_key?(acc, xy) do
+            %{acc | xy => max(Map.get(acc, xy) - 1, 0)}
+          else
+            acc
+          end
+        end)
+
+      "toggle" ->
+        Enum.reduce(change, lit, fn xy, acc ->
+          if Map.has_key?(acc, xy) do
+            %{acc | xy => Map.get(acc, xy) + 2}
+          else
+            Map.put(acc, xy, 2)
+          end
+        end)
+      end
+      adjust_brightness(updated, remaining)
+  end
+end
diff --git a/2015-elixir/lib/solutions/day_07.ex b/2015-elixir/lib/solutions/day_07.ex
new file mode 100644
index 0000000..abd8bb3
--- /dev/null
+++ b/2015-elixir/lib/solutions/day_07.ex
@@ -0,0 +1,22 @@
+defmodule Aoc.Solution.Day07 do
+  @name "Day 7: Some Assembly Required"
+  @behaviour Solution
+
+  @impl Solution
+  def get_name, do: @name
+
+  @impl Solution
+  def parse!(_raw) do
+    "10"
+  end
+
+  @impl Solution
+  def solve_first_part(_input) do
+    "(TBW)"
+  end
+
+  @impl Solution
+  def solve_second_part(_input) do
+    "(TBW)"
+  end
+end
diff --git a/2015-elixir/mix.exs b/2015-elixir/mix.exs
index 3af1c5c..54f358b 100644
--- a/2015-elixir/mix.exs
+++ b/2015-elixir/mix.exs
@@ -14,7 +14,7 @@ defmodule Aoc.MixProject do
   # Run "mix help compile.app" to learn about applications.
   def application do
     [
-      extra_applications: [:logger, :crypto]
+      extra_applications: [:logger]
     ]
   end
 
diff --git a/2015-elixir/test/day_06_test.exs b/2015-elixir/test/day_06_test.exs
new file mode 100644
index 0000000..c93cf05
--- /dev/null
+++ b/2015-elixir/test/day_06_test.exs
@@ -0,0 +1,45 @@
+defmodule Day06Test do
+  use ExUnit.Case
+  doctest Aoc.Solution.Day06
+  import Aoc.Solution.Day06
+
+  test "parses the input" do
+    input = """
+    turn off 674,321 through 793,388
+    toggle 749,672 through 973,965
+    turn on 943,30 through 990,907
+    """ |> String.trim()
+
+    expected = [
+      {"off", 674..793, 321..388},
+      {"toggle", 749..973, 672..965},
+      {"on", 943..990, 30..907},
+    ]
+
+    assert parse!(input) == expected
+  end
+
+  test "solves first part" do
+    input = """
+    turn on 0,0 through 999,999
+    toggle 0,0 through 999,0
+    turn off 499,499 through 500,500
+    """ |> String.trim()
+
+    a = input |> parse!() |> solve_first_part()
+
+    assert a == 998996
+  end
+
+  test "solves second part" do
+    input = """
+    turn on 0,0 through 999,999
+    toggle 0,0 through 999,0
+    turn off 499,499 through 500,500
+    """ |> String.trim()
+
+    a = input |> parse!() |> solve_second_part()
+
+    assert a == 1000000 + 2000 - 4
+  end
+end
diff --git a/2015-elixir/test/day_07_test.exs b/2015-elixir/test/day_07_test.exs
new file mode 100644
index 0000000..733dd9f
--- /dev/null
+++ b/2015-elixir/test/day_07_test.exs
@@ -0,0 +1,23 @@
+defmodule Day07Test do
+  use ExUnit.Case
+  doctest Aoc.Solution.Day07
+  import Aoc.Solution.Day07
+
+  test "parses the input" do
+    expected = 10
+
+    assert parse!("10") == expected
+  end
+
+  test "solves first part" do
+    a = "something" |> parse!() |> solve_first_part()
+
+    assert a == :something
+  end
+
+  test "solves second part" do
+    a = "something" |> parse!() |> solve_second_part()
+
+    assert a == :something
+  end
+end
diff --git a/2015-python/README.md b/2015-python/README.md
new file mode 100644
index 0000000..8715ad1
--- /dev/null
+++ b/2015-python/README.md
@@ -0,0 +1,29 @@
+Advent of Code 2021
+===================
+
+Solutions for #aoc2020 in Python 3 (3.8+).
+
+Help scripts
+------------
+
+Solve all puzzles:
+
+    python aoc.py
+    
+To bootstrap a new puzzle (creates `inputs/<day_no>.txt`, `solutions/day_<day_no>.py` och
+`tests/test_day_<day_no>.py`):
+
+    python aoc.py <dag_no> "<puzzle_name>"
+
+Manually copy the puzzle input from https://adventofcode.com and paste it in `inputs/<day_no>.txt`
+to start coding.
+
+Solve separate puzzle (replace `XX` with the puzzle number):
+
+    python -m solutions.day_XX
+
+Run tests (replace `XX` with the puzzle number):
+
+    python -m unittest --locals -v
+    # or, if `pytest` is preferred:
+    pytest
\ No newline at end of file
diff --git a/2015-python/aoc.py b/2015-python/aoc.py
new file mode 100644
index 0000000..aae6d95
--- /dev/null
+++ b/2015-python/aoc.py
@@ -0,0 +1,113 @@
+import sys
+
+year = 2021
+
+try:
+    _, day_no, name = sys.argv
+except ValueError:
+    day_no = None
+    name = None
+
+print(
+    f"\nAdvent of Code {year}"
+    "\n###################"
+    "\n\nby Anders Ytterström (@madr_se)"
+)
+
+if day_no and name:
+    print(f"\n- creating solutions/day_{day_no.zfill(2)}.py")
+    with open("solutions/day_{}.py".format(day_no.zfill(2)), "w") as s:
+        s.write(
+            """
+from solutions import BaseSolution
+
+
+class Solution(BaseSolution):
+    input_file = "{day_no}.txt"
+
+    def __str__(self):
+        return "Day {day}: {name}"
+
+    def parse_input(self, data):
+        return data
+
+    def solve(self, puzzle_input):
+        return True
+
+    def solve_again(self, puzzle_input):
+        return True
+
+
+if __name__ == "__main__":
+    solution = Solution()
+    solution.show_results()
+""".strip().format(
+                day=day_no, day_no=day_no.zfill(2), name=name
+            )
+            + "\n"
+        )
+    print(f"- creating tests/test_day_{day_no.zfill(2)}.py")
+    with open("tests/test_day_{}.py".format(day_no.zfill(2)), "w") as t:
+        t.write(
+            """
+import unittest
+
+from solutions.day_{day_no} import Solution
+
+
+class Day{day_no}TestCase(unittest.TestCase):
+    def setUp(self):
+        self.solution = Solution()
+        self.puzzle_input = self.solution.parse_input(
+            \"\"\"
+        <REPLACE ME>
+        \"\"\"
+        )
+
+    def test_parse_puzzle_input(self):
+        data = \"\"\"
+        <REPLACE ME>
+        \"\"\"
+        assert self.solution.parse_input(data) == "<REPLACE ME>"
+
+    # def test_solve_first_part(self):
+    #     assert self.solution.solve(self.puzzle_input) == True
+
+    # def test_solve_second_part(self):
+    #     assert self.solution.solve_again(self.puzzle_input) == True
+
+
+if __name__ == "__main__":
+    unittest.main()
+""".strip().format(
+                day_no=day_no.zfill(2)
+            )
+            + "\n"
+        )
+    print(f"- creating empty inputs/{day_no.zfill(2)}.txt")
+    with open("inputs/{}.txt".format(day_no.zfill(2)), "w") as i:
+        i.write("")
+
+    print(
+        f"""
+Done! start coding.
+
+Puzzle link:
+https://adventofcode.com/{year}/day/{day_no}
+
+Puzzle input (copy and paste to inputs/{day_no.zfill(2)}.txt):
+https://adventofcode.com/{year}/day/{day_no}/input
+    """
+    )
+    exit(0)
+
+for i in [str(n).zfill(2) for n in range(1, 26)]:
+    try:
+        solution = __import__(
+            "solutions.day_{}".format(i), globals(), locals(), ["Solution"], 0
+        ).Solution()
+        solution.show_results()
+    except IOError:
+        pass
+    except ImportError:
+        pass
diff --git a/2015-python/solutions/__init__.py b/2015-python/solutions/__init__.py
new file mode 100644
index 0000000..3810ab4
--- /dev/null
+++ b/2015-python/solutions/__init__.py
@@ -0,0 +1,32 @@
+class BaseSolution:
+    input_file = None
+    trim_input = True
+
+    def read_input(self, filename):
+        filepath = "./inputs/{}".format(filename)
+        with open(filepath, "r") as f:
+            data = f.read()
+            if self.trim_input:
+                return data.strip()
+            return data
+
+    def show_results(self):
+        data = self.read_input(self.input_file)
+        puzzle_input = self.parse_input(data)
+        print(
+            "\n\n{}\n{}\n\nPart 1: {}\nPart 2: {}".format(
+                str(self),
+                "-" * len(str(self)),
+                self.solve(puzzle_input),
+                self.solve_again(puzzle_input),
+            )
+        )
+
+    def solve(self, puzzle_input):
+        raise NotImplemented
+
+    def solve_again(self, puzzle_input):
+        raise NotImplemented
+
+    def parse_input(self, data):
+        raise NotImplemented
diff --git a/2015-python/solutions/day_06.py b/2015-python/solutions/day_06.py
new file mode 100644
index 0000000..f5ccd53
--- /dev/null
+++ b/2015-python/solutions/day_06.py
@@ -0,0 +1,22 @@
+from solutions import BaseSolution
+
+
+class Solution(BaseSolution):
+    input_file = "06.txt"
+
+    def __str__(self):
+        return "Day 6: Probably a Fire Hazard"
+
+    def parse_input(self, data):
+        return data
+
+    def solve(self, puzzle_input):
+        return True
+
+    def solve_again(self, puzzle_input):
+        return True
+
+
+if __name__ == "__main__":
+    solution = Solution()
+    solution.show_results()
diff --git a/2015-python/tests/__init__.py b/2015-python/tests/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/2015-python/tests/test_day_06.py b/2015-python/tests/test_day_06.py
new file mode 100644
index 0000000..aeb9aef
--- /dev/null
+++ b/2015-python/tests/test_day_06.py
@@ -0,0 +1,29 @@
+import unittest
+
+from solutions.day_06 import Solution
+
+
+class Day06TestCase(unittest.TestCase):
+    def setUp(self):
+        self.solution = Solution()
+        self.puzzle_input = self.solution.parse_input(
+            """
+        <REPLACE ME>
+        """
+        )
+
+    def test_parse_puzzle_input(self):
+        data = """
+        <REPLACE ME>
+        """
+        assert self.solution.parse_input(data) == "<REPLACE ME>"
+
+    # def test_solve_first_part(self):
+    #     assert self.solution.solve(self.puzzle_input) == True
+
+    # def test_solve_second_part(self):
+    #     assert self.solution.solve_again(self.puzzle_input) == True
+
+
+if __name__ == "__main__":
+    unittest.main()