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Game pieces: the Things in your game

A basket, a ball, a brick, a hopping bird. Every game is made of pieces. In the arcade each one is a Thing: a piece that remembers where it is and can draw itself.

The big idea

A Thing is a game piece. It keeps its own x, y, size, and color, and it has built-in actions like .draw() and .move().

See it in code

1Start simple

One line makes a Thing. Its keywords say where it starts, how big it is, and its color. After that, basket.draw() paints it:

python
basket = Thing(x=320, y=420, width=100, height=24, color="teal")

def play():
    pass

def draw():
    paper("misty rose")
    rect(x=320, y=455, width=640, height=50, color="burlywood")
    basket.draw()
A basket, made from one Thing:
A pink game window with a wooden counter and a wide teal basket sitting just above it in the middle.

pass means "do nothing." This game has no rules yet. Programmers call a game piece like this a sprite.

2A step further

A Thing can be a box, a circle, or an oval. Each one keeps its own numbers, so changing ball.x moves only the ball:

python
paddle = Thing(x=40, y=240, width=16, height=90, color="white")
ball = Thing(x=120, y=240, size=20, color="white", shape="circle")
blimp = Thing(x=320, y=90, width=140, height=50, color="orange", shape="oval")

def play():
    ball.x = ball.x + 4

def draw():
    paper("navy")
    paddle.draw()
    ball.draw()
    blimp.draw()
Three pieces, three shapes, and only the ball is moving:
A navy game window with a white paddle on the left, a white ball that has moved to the right, and an orange oval near the top.

size=20 is a shortcut that sets the width and the height together. The dot in ball.x means "the x that belongs to the ball."

3In the arcade

A plain circle is a bit dull for a cupcake. Write a recipe that draws real shapes at the Thing's spot. The Thing still does the remembering:

python
basket = Thing(x=320, y=420, width=100, height=24, color="teal")
cupcake = Thing(x=250, y=-20, size=40, color="orchid", shape="circle")
wrapper_drop = 13
cherry_lift = 19

def draw_cupcake():
    box(x=cupcake.x, y=cupcake.y + wrapper_drop, width=34, height=22, color="peru", corner=4)
    circle(x=cupcake.x, y=cupcake.y, size=40, color=cupcake.color)
    circle(x=cupcake.x, y=cupcake.y - cherry_lift, size=12, color="red")

def play():
    cupcake.y = cupcake.y + 3

def draw():
    paper("misty rose")
    rect(x=320, y=455, width=640, height=50, color="burlywood")
    draw_cupcake()
    basket.draw()
A falling cupcake with a wrapper and a cherry:
A bakery scene with a detailed cupcake falling through the air: a brown wrapper, purple frosting, and a red cherry on top, above a teal basket.

Every shape in the recipe is measured from cupcake.x and cupcake.y. When the Thing falls, the wrapper, frosting, and cherry all fall with it.

The same idea, everywhere

Any game piece works this way, whatever it looks like. A brick, a rock, a laser, and a snake's body are all Things with a spot, a size, and a way to be drawn.

Try it yourself

Change color="orchid" in the cupcake's Thing to "hot pink" and run it. The frosting changes, because the recipe reads cupcake.color. Then add a second cherry.

The common mistake

Forgetting to draw a piece. Making a Thing doesn't put it on screen. If a piece is missing, check that draw() calls its .draw() or its drawing recipe.

What it unlocks

Pieces come alive when they move, when the player steers them, and when they touch each other.

Related concepts