Coordinate system

Simulation: origin at the top left

Game logic uses a y-down coordinate system: (0, 0) is the top-left corner, x increases to the right, and y increases downwards. Entity positions are their centers. For the ball, positive speed.y moves down and negative speed.y moves up.

Rectangles derive their edges from the center:

• left = pos_x - width / 2
• right = pos_x + width / 2
• top = pos_y - height / 2
• bottom = pos_y + height / 2

Rendering: origin at the bottom left

Arcade uses y-up coordinates. Entity rendering flips the vertical position against the window height: a center at simulation y-coordinate y is rendered at window_height - y. For rectangles, each y-down edge is similarly converted before drawing. Collision checks remain entirely in simulation coordinates.