Title, Pause & Game Over Screens

By the end of this lesson you can:

• Extend a two-state game-state machine (PZ-31) to four states: "title", "play", "pause", "game_over".
• Write a separate draw function for each state so draw() stays clean and readable.
• Handle clean transitions between states, resetting the game when the player restarts.

In PZ-31 you built a two-state game: "play" and "game_over". Quick check — what does this print?

state = "play"

if state == "play":
    print("Game running")
elif state == "game_over":
    print("Game over screen")
else:
    print("Unknown state")

Game running

Think of a state machine like the indicator light on a vending machine: it shows one thing at a time — "insert coin", "choose item", "dispensing", "sold out". It cannot be in two states at once, and pressing buttons only makes sense in certain states.

The four states and when they occur

• "title" — game has not started. Show the game name and "Press SPACE to play".
• "play" — game is active. Run physics, input, scoring.
• "pause" — player pressed P. Freeze everything; show "PAUSED — press P to resume".
• "game_over" — lives hit zero. Show score and "Press R to restart".

Clean draw() using helpers

def draw():
    screen.fill("black")
    if state == "title":
        draw_title()
    elif state == "play":
        draw_play()
    elif state == "pause":
        draw_play()        # show frozen game behind
        draw_pause_overlay()
    elif state == "game_over":
        draw_game_over()

The pause state calls draw_play() first, then overlays the pause message. The player can see their frozen game behind the banner — that is the standard pattern.

Clean update() using helpers

def update():
    if state == "play":
        update_play()

update() only runs game logic when in the "play" state. Other states freeze the simulation.

Transitions via on_key_down()

def on_key_down(key):
    global state
    if state == "title" and key == keys.SPACE:
        reset_game()
        state = "play"
    elif state == "play" and key == keys.P:
        state = "pause"
    elif state == "pause" and key == keys.P:
        state = "play"
    elif state == "game_over" and key == keys.R:
        reset_game()
        state = "title"

The story

Wei Jie extends his catcher game to have a proper title screen, a pause, and a game-over screen. Save as four_states.py.

# four_states.py — full four-state game loop
import pgzrun
import random

WIDTH = 480
HEIGHT = 320
TITLE = "Durian Dash"

state = "title"
score = 0
lives = 3
ball_x = 240
ball_y = -30
BALL_SPEED = 4

def reset_game():
    global score, lives, ball_x, ball_y
    score = 0
    lives = 3
    ball_x = random.randint(30, WIDTH - 30)
    ball_y = -30

def update_play():
    global ball_y, ball_x, lives, state
    ball_y += BALL_SPEED
    if ball_y > HEIGHT + 30:
        lives -= 1
        ball_y = -30
        ball_x = random.randint(30, WIDTH - 30)
        if lives <= 0:
            state = "game_over"

def on_mouse_down(pos, button):
    global score, ball_y, ball_x
    if state != "play":
        return
    dist = ((pos[0] - ball_x) ** 2 + (pos[1] - ball_y) ** 2) ** 0.5
    if dist < 28:
        score += 1
        ball_y = -30
        ball_x = random.randint(30, WIDTH - 30)

def on_key_down(key):
    global state
    if state == "title" and key == keys.SPACE:
        reset_game()
        state = "play"
    elif state == "play" and key == keys.P:
        state = "pause"
    elif state == "pause" and key == keys.P:
        state = "play"
    elif state == "game_over" and key == keys.R:
        state = "title"

def draw_title():
    screen.draw.text("DURIAN DASH", center=(240, 120), fontsize=52, color="gold")
    screen.draw.text("Press SPACE to play", center=(240, 200), fontsize=24, color="white")

def draw_play():
    screen.draw.filled_circle((ball_x, ball_y), 26, "crimson")
    screen.draw.text(f"Score: {score}  Lives: {lives}",
                     topleft=(10, 10), fontsize=22, color="white")

def draw_pause_overlay():
    r = Rect((90, 110), (300, 80))
    screen.draw.filled_rect(r, (0, 0, 0))
    screen.draw.rect(r, (255, 255, 255))
    screen.draw.text("PAUSED", center=(240, 135), fontsize=36, color="white")
    screen.draw.text("Press P to resume", center=(240, 170), fontsize=20, color="grey")

def draw_game_over():
    screen.draw.text("GAME OVER", center=(240, 110), fontsize=48, color="crimson")
    screen.draw.text(f"Final score: {score}", center=(240, 175), fontsize=28, color="white")
    screen.draw.text("Press R to return to title", center=(240, 220), fontsize=20, color="grey")

def update():
    if state == "play":
        update_play()

def draw():
    screen.fill("black")
    if state == "title":
        draw_title()
    elif state == "play":
        draw_play()
    elif state == "pause":
        draw_play()
        draw_pause_overlay()
    elif state == "game_over":
        draw_game_over()

pgzrun.go()

Extending a state machine from two states to four is straightforward: add new string constants, new elif branches in draw() and update(), and new key bindings in on_key_down(). Always call reset_game() before entering "play" so leftover data from a previous run is cleared. Keep each state's draw logic in its own helper function to stay readable.