diff --git a/blokus.py b/blokus.py
index 30c20ed..d55d872 100755
--- a/blokus.py
+++ b/blokus.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+from typing import Any
 import numpy as np
 import random
 
@@ -37,8 +38,8 @@ tiles = [
 ]
 
 
-def get_permutations(which_tiles: list[int]):
-    permutations = []
+def get_permutations(which_tiles: list[int]) -> list[tuple[int, np.ndarray]]:
+    permutations: list[tuple[int, np.ndarray]] = []
 
     for i, tile in enumerate(tiles):
         if i not in which_tiles:
@@ -48,7 +49,7 @@ def get_permutations(which_tiles: list[int]):
         flips = [np.flip(r, axis=1) for r in rots]  # flip horizontally
         all_orients = rots + flips  # 8 orientations
 
-        seen = set()
+        seen: set[tuple[Any, bytes]] = set()
         for t in all_orients:
             key = (t.shape, t.tobytes())
             if key not in seen:
@@ -58,8 +59,10 @@ def get_permutations(which_tiles: list[int]):
     return permutations
 
 
-def can_place(board, tile, player):
-    placements = []
+def can_place(
+    board: np.ndarray, tile: np.ndarray, player: int
+) -> list[tuple[int, int]]:
+    placements: list[tuple[int, int]] = []
     has_minus_one = False
     for x in range(BOARD_SIZE):
         for y in range(BOARD_SIZE):
@@ -85,7 +88,7 @@ def can_place(board, tile, player):
                             break
                 else:
                     placements.append((x, y))
-    final = []
+    final: list[tuple[int, int]] = []
     if has_minus_one:
         for x, y in placements:
             with np.nditer(tile, flags=["multi_index"]) as it:
@@ -130,7 +133,14 @@ def can_place(board, tile, player):
     return final
 
 
-def do_placement(tidx, tile, placement, game_state, player):
+def do_placement(
+    tidx: int,
+    tile: np.ndarray,
+    placement: tuple[int, int],
+    game_state: tuple[np.ndarray, list[int], list[int]],
+    player: int,
+):
+    assert player > 0
     (x, y) = placement
     with np.nditer(tile, flags=["multi_index"]) as it:
         for v in it:
@@ -140,7 +150,7 @@ def do_placement(tidx, tile, placement, game_state, player):
     game_state[player].remove(tidx)
 
 
-def print_game_state(game_state):
+def print_game_state(game_state: tuple[np.ndarray, list[int], list[int]]):
     (board, p1tiles, p2tiles) = game_state
 
     for row in board:
@@ -169,6 +179,7 @@ playing = True
 player = 1
 while playing:
     moves = []
+    assert player > 0
     for tidx, tile in get_permutations(game_state[player]):
         for placement in can_place(game_state[0], tile, player):
             moves.append((tidx, tile, placement))