Viewport edge scroll

Goal

Keep a fixed-size window into an infinite world; scroll when the dot reaches the edge.

Viewport state

Track viewport.x and viewport.y (world coordinates of the top-left corner). Render at:

screenX = worldX - viewport.x
screenY = worldY - viewport.y

Edge detection

When the local dot's screen position is within EDGE_MARGIN pixels of any edge, shift the viewport:

if (localX < margin) viewport.x -= SCROLL_SPEED
if (localX > width - margin) viewport.x += SCROLL_SPEED
// same for Y

This is client-only — no server calls required.

Exit criteria

• Single player can move beyond the initial view bounds

Next: Collaborative viewport