diff --git a/.editorconfig b/.editorconfig
new file mode 100644
index 0000000..f1fdf64
--- /dev/null
+++ b/.editorconfig
@@ -0,0 +1,24 @@
+# \file   .editorconfig
+# \author Copyright 2020, Matthew Gretton-Dann
+# SPDX-License-Identifier: Apache-2.0
+
+# top-most EditorConfig file
+root = true
+
+# We default to 2-spaces at tabs
+[*]
+indent_style = space
+indent_size = 2
+tab_width = 8
+trim_trailing_whitespace = true
+insert_final_newline = true
+max_line_length = 100
+
+# Python is 4 spaces
+[*.py]
+indent_size = 4
+max_line_length = 79
+
+# Makefiles use Tabs.
+[Makefile]
+indent_style = tab
diff --git a/CMakeLists.txt b/CMakeLists.txt
index e51380b..afd0ef3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -5,17 +5,19 @@ set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
-file(GLOB years LIST_DIRECTORIES true RELATIVE "${CMAKE_SOURCE_DIR}" CONFIGURE_DEPENDS "20[1-9][0-9]")
+file(GLOB years LIST_DIRECTORIES true RELATIVE "${CMAKE_SOURCE_DIR}" CONFIGURE_DEPENDS
+        "20[1-9][0-9]")
 message(STATUS "Years to examine: ${years}")
-foreach(year IN LISTS years)
-    file(GLOB puzzles RELATIVE "${CMAKE_SOURCE_DIR}" CONFIGURE_DEPENDS "${year}/puzzle-*.cc")
-    foreach(puzzle IN LISTS puzzles)
-        string(REGEX REPLACE "^.*puzzle-(.*)\\.cc" "puzzle-${year}-\\1" puzzle_name "${puzzle}")
-        string(REGEX REPLACE "^.*puzzle-(.*)\\.cc" "${CMAKE_SOURCE_DIR}/${year}/puzzle-\\1.CMakeLists.txt" sub_cmake_lists "${puzzle}")
-        message(STATUS "Puzzle: ${puzzle_name} - source ${puzzle}")
-        add_executable("${puzzle_name}" "${puzzle}")
-        if(EXISTS "${sub_cmake_lists}")
-            include("${sub_cmake_lists}")
-        endif()
-    endforeach()
-endforeach()
\ No newline at end of file
+foreach (year IN LISTS years)
+  file(GLOB puzzles RELATIVE "${CMAKE_SOURCE_DIR}" CONFIGURE_DEPENDS "${year}/puzzle-*.cc")
+  foreach (puzzle IN LISTS puzzles)
+    string(REGEX REPLACE "^.*puzzle-(.*)\\.cc" "puzzle-${year}-\\1" puzzle_name "${puzzle}")
+    string(REGEX REPLACE "^.*puzzle-(.*)\\.cc"
+            "${CMAKE_SOURCE_DIR}/${year}/puzzle-\\1.CMakeLists.txt" sub_cmake_lists "${puzzle}")
+    message(STATUS "Puzzle: ${puzzle_name} - source ${puzzle}")
+    add_executable("${puzzle_name}" "${puzzle}")
+    if (EXISTS "${sub_cmake_lists}")
+      include("${sub_cmake_lists}")
+    endif ()
+  endforeach ()
+endforeach ()
diff --git a/README.md b/README.md
index a74590f..77bfec9 100644
--- a/README.md
+++ b/README.md
@@ -1,11 +1,12 @@
 # C++ Solutions to Advent of Code
 
-This repository contains solutions to various years of the [Advent of Code](https://adventofcode.com)
-puzzles.  All solutions are written in C++.  The solutions aren't designed to be nice or
-pretty.  Instead, I am using it as an experiment in understanding how I approach solving
-problems.
+This repository contains solutions to various years of
+the [Advent of Code](https://adventofcode.com)
+puzzles. All solutions are written in C++. The solutions aren't designed to be nice or pretty.
+Instead, I am using it as an experiment in understanding how I approach solving problems.
 
-The solutions are authored by Matthew Gretton-Dann, and Copyright 2020-2021, Matthew Gretton-Dann.  Licensed under Apache 2.0 - see [license](./LICENSE).
+The solutions are authored by Matthew Gretton-Dann, and Copyright 2020-2021, Matthew Gretton-Dann.
+Licensed under Apache 2.0 - see [license](./LICENSE).
 
 ## Getting the sources
 
@@ -19,14 +20,14 @@ git clone https://github.com/matt-gretton-dann/advent-of-code/
 
 The following is required to build the puzzles:
 
- * CMake
- * C++20 compiler
- * OpenSSL headers.
+* CMake
+* C++20 compiler
+* OpenSSL headers.
 
 ## Running the Puzzles
 
-There is a driver script (`./driver.sh`) in the root of the checkout.  It will build and run specific tests.  Example
-use is as follows:
+There is a driver script (`./driver.sh`) in the root of the checkout. It will build and run specific
+tests. Example use is as follows:
 
 ```sh
 YEAR=2020 # Year of puzzle to run
@@ -45,7 +46,10 @@ cmake -Bbuild -S.
 cmake --build build
 ```
 
-Note that some of the puzzles require OpenSSL for the MD5 implementation.  On macOS this also requires you to pass an appropariate value for `OPENSSL_ROOT_DIR` to cmake.  On x86 this is `-DOPENSSL_ROOT_DIR=/usr/local/opt/openssl` and on AArch64 this is `-DOPENSSL_ROOT_DIR=/opt/homebrew/opt/openssl`.
+**Note**: Some puzzles require OpenSSL for the MD5 implementation. On macOS this requires you to
+pass an appropriate value for `OPENSSL_ROOT_DIR` to `cmake`. If using `homebrew` then x86 this
+is `-DOPENSSL_ROOT_DIR=/usr/local/opt/openssl` and on AArch64 this
+is `-DOPENSSL_ROOT_DIR=/opt/homebrew/opt/openssl`.
 
 ## Sources
 
@@ -53,19 +57,20 @@ All code is written in C++.
 
 ### Directory Layout
 
-Each year of puzzles is in a self-contained directory `YEAR`.  
+Each year of puzzles is in a self-contained directory `YEAR`.
 
 Within the directory there are the following files:
 
- * `puzzle-DAY-NUMBER.cc`.  The source for puzzle NUMBER on day DAY in the year.
- * `driver-DAY-NUMBER.sh`.  If present this is used as the driver to run that puzzle.
- * `puzzle-DAY-NUMBER.CMakeLists.txt`.  If present this is included by `CMakeLists.txt`.  The variable `${puzzle_name}`
-   contains the name of the puzzle target.  Some puzzles use this to depend on OpenSSL. 
+* `puzzle-DAY-NUMBER.cc`. The source for puzzle NUMBER on DAY in the year.
+* `driver-DAY-NUMBER.sh`. If present this is used as the driver to run that puzzle.
+* `puzzle-DAY-NUMBER.CMakeLists.txt`. If present this is included by `CMakeLists.txt`. The
+  variable `${puzzle_name}`
+  contains the name of the puzzle target. Some puzzles use this to depend on OpenSSL.
 
 ### Command Line Interface
 
 The executable command line interface should just take the input in on standard-input and print its
 result on standard-output.
 
-If this is not possible the script `driver-DAY-NUMBER.sh` within the year directory should be provided.  It should take
-two arguments - the executable to run and the input file to use.
\ No newline at end of file
+If this is not possible the script `driver-DAY-NUMBER.sh` within the year directory should be
+provided. It should take two arguments - the executable to run and the input file to use.
diff --git a/driver.sh b/driver.sh
index 50be12e..c696f91 100755
--- a/driver.sh
+++ b/driver.sh
@@ -44,8 +44,8 @@ fi
 # Rebuild the executable we want to run.
 if [ ! -d "build" ]; then
     opts=
-    if [ "$(uname -s)" == "Darwin" ]; then
-      if [ "$(uname -m)" == "arm64" ]; then
+    if [ "$(uname -s)" = "Darwin" ]; then
+      if [ "$(uname -m)" = "arm64" ]; then
         opts="-DOPENSSL_ROOT_DIR=/opt/homebrew/opt/openssl"
       else
         opts="-DOPENSSL_ROOT_DIR=/usr/local/opt/openssl"