diff --git a/.gitignore b/.gitignore
index 00c1844..8315cca 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-.direnv/
\ No newline at end of file
+.direnv/
+/result
\ No newline at end of file
diff --git a/000-999/144/main.py b/000-999/144/main.py
deleted file mode 100644
index 55189e2..0000000
--- a/000-999/144/main.py
+++ /dev/null
@@ -1,15 +0,0 @@
-def rot13(message):
-    subs = {'A': 'N', 'B': 'O', 'C': 'P', 'D': 'Q', 'E': 'R', 'F': 'S', 'G': 'T', 'H': 'U', 'I': 'V', 'J': 'W', 'K': 'X', 'L': 'Y', 'M': 'Z', 'N': 'A', 'O': 'B', 'P': 'C', 'Q': 'D', 'R': 'E', 'S': 'F', 'T': 'G', 'U': 'H', 'V': 'I', 'W': 'J', 'X': 'K', 'Y': 'L', 'Z': 'M',
-            'a': 'N', 'b': 'O', 'c': 'P', 'd': 'Q', 'e': 'R', 'f': 'S', 'g': 'T', 'h': 'U', 'i': 'V', 'j': 'W', 'k': 'X', 'l': 'Y', 'm': 'Z', 'n': 'A', 'o': 'B', 'p': 'C', 'q': 'D', 'r': 'E', 's': 'F', 't': 'G', 'u': 'H', 'v': 'I', 'w': 'J', 'x': 'K', 'y': 'L', 'z': 'M'}
-
-    return ''.join(list(map(
-        lambda x: subs[x] if x in subs else x,
-        message
-    )))
-
-
-if __name__ == '__main__':
-    with open('./000-999/144/inputs/input') as file:
-        input = file.read()
-
-    print(rot13(input))
diff --git a/README.md b/README.md
index 17a5d43..f20b1ac 100644
--- a/README.md
+++ b/README.md
@@ -7,4 +7,4 @@ The folder name is the challenge id, as found in the URL (<https://play.picoctf.
 
 Inside the folder there is an `inputs` subfolder which just includes all the files from the challenge description.
 
-Executing `main.py` runs the challenge.
+Executing `nix run .#CHALLENGE_ID` runs the challenge.
diff --git a/000-999/144/inputs/input b/exercises/144/inputs/input
similarity index 100%
rename from 000-999/144/inputs/input
rename to exercises/144/inputs/input
diff --git a/exercises/144/main.py b/exercises/144/main.py
new file mode 100644
index 0000000..7607979
--- /dev/null
+++ b/exercises/144/main.py
@@ -0,0 +1,15 @@
+def rot13(message):
+    alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+    subs = {char: alphabet[(i + 13) % 26] for i, char in enumerate(alphabet)}
+
+    return ''.join(list(map(
+        lambda x: subs[x] if x in subs else x,
+        message
+    )))
+
+
+if __name__ == '__main__':
+    with open("./exercises/144/inputs/input") as file:
+        input = file.read()
+
+    print(rot13(input))
diff --git a/000-999/147/info.nix b/exercises/147/info.nix
similarity index 100%
rename from 000-999/147/info.nix
rename to exercises/147/info.nix
diff --git a/000-999/147/inputs/flag b/exercises/147/inputs/flag
similarity index 100%
rename from 000-999/147/inputs/flag
rename to exercises/147/inputs/flag
diff --git a/000-999/147/main.py b/exercises/147/main.py
similarity index 57%
rename from 000-999/147/main.py
rename to exercises/147/main.py
index ec4241c..bedf768 100644
--- a/000-999/147/main.py
+++ b/exercises/147/main.py
@@ -1,5 +1,5 @@
 if __name__ == '__main__':
-    with open('./000-999/147/inputs/flag') as file:
+    with open('./exercises/147/inputs/flag') as file:
         input = file.read()
 
     print(input)
diff --git a/flake.nix b/flake.nix
index 48362fa..99f0e0d 100644
--- a/flake.nix
+++ b/flake.nix
@@ -11,11 +11,37 @@
   }: let
     system = "x86_64-linux";
     pkgs = nixpkgs.legacyPackages.${system};
+
+    exercises = builtins.attrNames (builtins.readDir ./exercises);
+    forAllExercises = nixpkgs.lib.genAttrs exercises;
   in {
     formatter.${system} = pkgs.alejandra;
 
-    devShells.${system}.default = pkgs.mkShellNoCC {
-      packages = with pkgs; [python3];
-    };
+    packages.${system} = forAllExercises (
+      exercise:
+        pkgs.writers.writePython3Bin "picoCTF_${exercise}" {
+          # libraries = with pkgs.python3.pkgs; [ requests ];
+        } "${builtins.readFile ./exercises/${exercise}/main.py}"
+    );
+
+    apps.${system} = forAllExercises (
+      exercise: {
+        type = "app";
+        program = "${self.packages.${system}.${exercise}}/bin/picoCTF_${exercise}";
+      }
+    );
+
+    devShells.${system} =
+      forAllExercises (
+        exercise:
+          pkgs.mkShellNoCC {
+            packages = with pkgs; [python3];
+          }
+      )
+      // {
+        default = pkgs.mkShellNoCC {
+          packages = with pkgs; [python3];
+        };
+      };
   };
 }