Quickstep

A gap gets you into the lane. The next gap gets you out. Cross two banks of moving traffic, pause on the halfway strip and reach the marked exit at the top.

Use I/J/K/L for up, left, down and right. Traffic keeps moving while you wait. R retries the same pattern, Q quits and S starts from the title. A cell must be clear before traffic moves and remain safe afterwards; a vehicle about to leave does not make its cell available early.

Quickstep runs in Sinclair BASIC on a stock 48K ZX Spectrum. It is silent, with six predictable lanes and one crossing to complete. The dotted strips are safe places to plan. In a lane, waiting is a decision with consequences.

From one lane to a crossing

Begin a new program with the person and two strips of ground. Add single-step movement, then vehicles you advance yourself. A clock makes traffic independent of your keys; two contact checks turn the practice board into a small game.

Arrays expand that game into the full crossing. We then investigate routes, retain a short key press during drawing, add opening instructions and save a self-starting tape. Each lesson explains the BASIC it uses. Ten lessons use eight runnable programs: route planning and saving reuse a checkpoint already built.