Step 01 — Vectors

You know this cold. The point of this step is to make the red→green loop automatic, not to teach you arithmetic. Blast through it.

Concept

A vector here is nothing mystical: a pair of numbers (x, y). We use the same value to mean two different things depending on context:

a position — a point in the world.
a displacement / velocity — an arrow: "move this much in x, this much in y."

That's it. All of 2D physics is built on adding, subtracting, and scaling these pairs.

add(a, b) → (a.x + b.x, a.y + b.y) — apply an arrow to a point.
sub(a, b) → (a.x - b.x, a.y - b.y) — the arrow that points from b to a.
scale(a, s) → (a.x * s, a.y * s) — make an arrow longer/shorter.

Note: we return new objects (pure functions) here for clarity. Your real engine mutates vectors in place to avoid garbage collection — that's a speed optimization we'll deliberately ignore until the very end.

Task

Implement vec, add, sub, and scale in vector.ts.

bun test workshop/steps/01-vectors