add tetris challenge

functions/function_parameters.rst

@@ -50,16 +50,30 @@ Here is a small illustration:
    print("The list now contains", data)
    print("The number is now", number)
 
-----
-
-Good function style
--------------------
-
--  Arguments for input only.
--  Return statement for output only.
--  No global variables.
--  One function serves exactly one purpose.
--  Write documentation string first.
--  keep functions small (below one screen page)
--  If you have too many parameters, make a new class.
--  Do not mix mutable types and return output.
+
+.. topic:: Good function style
+
+   -  Arguments for input only.
+   -  Return statement for output only.
+   -  No global variables.
+   -  One function serves exactly one purpose.
+   -  Write documentation string first.
+   -  keep functions small (below one screen page)
+   -  If you have too many parameters, make a new class.
+   -  Do not mix mutable types and return output.
+
+Challenge: Refactor existing code into functions
+------------------------------------------------
+
+.. image:: tetris.png
+
+In :download:`tetris.py`, you find a complete Tetris game.
+It makes heavy use of the Numpy library.
+The code almost has no structure.
+
+Create functions with reasonable names to make the code cleaner.
+
+.. note::
+
+   There is also a bug when dropping long bricks to the ground.
+   Maybe the refactoring makes this issue easier to debug.

functions/tetris.py

@@ -0,0 +1,127 @@
+"""
+Tetris
+
+Install dependencies:
+
+    pip install opencv-python
+"""
+import numpy as np
+import cv2
+import random
+
+ROWS, COLS = 17, 10
+TILE_SIZE = 32
+SCREEN_SIZE_X, SCREEN_SIZE_Y = COLS * TILE_SIZE, ROWS * TILE_SIZE
+
+# box with three extra layers of wall for rotations and moves
+box = np.ones((ROWS + 2, COLS + 4), dtype=np.uint8)
+box[:-3, 3:-3] = 0
+
+# definition of bricks
+BRICKS = [
+    """
+.#.
+###
+...
+""", """
+.#.
+##.
+#..
+""", """
+.#.
+.##
+..#
+""", """
+.##
+.#.
+.#.
+""", """
+##.
+.#.
+.#.
+""", """
+##
+##
+""", """
+..#.
+..#.
+..#.
+..#.
+""", """
+#.
+#.
+"""
+]
+BRICKS = [
+    (np.array([list(row) for row in b.strip().split()]) == "#").astype(np.uint8)
+    for b in BRICKS
+]
+
+
+# create first brick
+brick = random.choice(BRICKS)
+x, y = 5, 0
+
+timer = 150
+box_full = False
+while not box_full:
+
+    # draw everything
+    frame = np.zeros((SCREEN_SIZE_Y, SCREEN_SIZE_X, 3), np.uint8)
+    box_cut = box[:-2, 2:-2]
+    bb = np.kron(box_cut, np.ones((TILE_SIZE, TILE_SIZE), dtype=np.uint8)) * 192
+    frame[:,:,0] = bb
+    frame[:,:,1] = bb
+    frame[:,:,2] = bb
+
+    br = np.kron(brick, np.ones((TILE_SIZE, TILE_SIZE), dtype=np.uint8)) * 255
+    frame[y*TILE_SIZE:y*TILE_SIZE+br.shape[0], (x-2)*TILE_SIZE:(x-2)*TILE_SIZE+br.shape[1],0] += br
+
+    cv2.imshow("Tetris", frame)
+
+    # handle keyboard input
+    key = chr(cv2.waitKey(1) & 0xFF)
+    newbrick = brick
+    newx, newy = x, y
+    if key == "d":
+        newx += 1
+    elif key == "a":
+        newx -= 1
+    elif key == "s":
+        newy += 1
+    elif key == "w":
+        newbrick = brick.T[::-1]  # swap x & y, then mirror y
+    elif key == "q":
+        box_full = True
+
+    # place brick in new position if it does not collide
+    check = box.copy()
+    check[newy:newy+newbrick.shape[0], newx:newx+newbrick.shape[1]] += newbrick
+    if not (check == 2).any():
+        brick = newbrick
+        x, y = newx, newy
+
+    timer -= 1
+    if timer == 0:
+        # brick drops automatically
+        timer = 150
+        y += 1
+        check = box.copy()
+        check[y:y+brick.shape[0], newx:newx+brick.shape[1]] += brick
+        if (check == 2).any():
+            # brick stops moving, place it in the box
+            if y == 1:
+                box_full = True
+            y -= 1
+            box[y:y+brick.shape[0], newx:newx+brick.shape[1]] += brick
+
+            # remove rows
+            for row in range(box.shape[0] - 3):
+                if box[row].sum() == box.shape[1]:
+                    box[1:row + 1] = box[:row]
+                    box[0, 3:-3] = 0
+
+            x, y = 4, 0
+            brick = random.choice(BRICKS)
+
+cv2.destroyAllWindows()