diff --git a/cd/__init__.py b/cd/__init__.py
index a23ea49..75b010d 100644
--- a/cd/__init__.py
+++ b/cd/__init__.py
@@ -1,3 +1,5 @@
+"""Continuous Deployment."""
+
 import os
 from pathlib import Path
 
@@ -71,19 +73,19 @@ def browse(root: str) -> None:
             absolute_path = Path(directory) / file
             relative_path = os.path.relpath(absolute_path, start=root)
             paths.append(relative_path)
-    open(root)
+    frame(root)
     for path in sorted(paths):
         print(path)
     shut(root)
 
 
 def cat(file: str) -> None:
-    open(file)
+    frame(file)
     print(fs.read_file_text(file).rstrip())
     shut(file)
 
 
-def install_commands(path) -> None:
+def install_commands(path: str) -> None:
     step("Install commands")
     user = Path("/usr/local/bin")
     for command in [
@@ -94,10 +96,10 @@ def install_commands(path) -> None:
         "synchronize",
     ]:
         print(command)
-        os.symlink(path, user / f"{COMMANDS_PREFIX}{command}")
+        (user / f"{COMMANDS_PREFIX}{command}").symlink_to(path)
 
 
-def set_ssh(*arguments) -> None:
+def set_ssh(*arguments: str) -> None:
     step("Set SSH")
     #
     ssh_key, ssh_hosts = arguments
@@ -124,12 +126,12 @@ def set_ssh(*arguments) -> None:
     cat(known)
 
 
-def open(*arguments) -> None:
+def frame(*arguments: str) -> None:
     print(env.CD_OPEN, end="")
     print(*arguments, flush=True)
 
 
-def shut(*arguments) -> None:
+def shut(*arguments: str) -> None:
     print(env.CD_SHUT, end="")
     print(*arguments, flush=True)
 
@@ -138,7 +140,7 @@ def split() -> None:
     print(env.CD_SPLT, flush=True)
 
 
-def step(*arguments) -> None:
+def step(*arguments: str) -> None:
     env.CD_STEP += 1
     print(env.CD_DOWN)
     print(env.CD_VERT, env.CD_STEP, *arguments)
diff --git a/cd/__main__.py b/cd/__main__.py
index 891e6aa..520006a 100755
--- a/cd/__main__.py
+++ b/cd/__main__.py
@@ -1,17 +1,18 @@
 #! /usr/bin/env python3
 
+"""Entry point to either bootstrap or command."""
+
 import sys
 from pathlib import Path
 
 import cd
 
 if __name__ == "__main__":
-    command, *arguments = sys.argv
-    command = Path(command).name
-    if command == "__main__.py":
+    path, *arguments = sys.argv
+    name = Path(path).name
+    if name == "__main__.py":
         cd.set_ssh(*arguments)
         cd.install_commands(__file__)
     else:
-        command = command.replace("-", "_")
-        function = getattr(cd, command)
+        function = getattr(cd, name.replace("-", "_"))
         function(*arguments)
diff --git a/cd/project.py b/cd/project.py
index 51971d1..bdb2426 100644
--- a/cd/project.py
+++ b/cd/project.py
@@ -1,4 +1,10 @@
+from __future__ import annotations
+
 from pathlib import Path
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from cd.projects import Projects
 
 BRANCH = [
     "GITHUB_REF_NAME",
@@ -15,7 +21,7 @@ ROOT = [
 
 
 class Project:
-    def __init__(self, projects) -> None:
+    def __init__(self: Project, projects: Projects) -> None:
         self.projects = projects
         # branch
         for variable in BRANCH:
diff --git a/cd/projects.py b/cd/projects.py
index 9094c20..a1ca31f 100644
--- a/cd/projects.py
+++ b/cd/projects.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pathlib import Path
 
 GROUP_AND_NAME = [
@@ -11,7 +13,7 @@ SERVER_URL = [
 
 
 class Projects:
-    def __init__(self, environment) -> None:
+    def __init__(self: Projects, environment) -> None:
         self.environment = environment
         # group, name
         for variable in GROUP_AND_NAME: