A draw-then-watch puzzle prototype where one stroke is the whole solution, and the failure shows exactly where it went wrong.
The player drags one stroke across the gap; the budget meter drains as the line grows and the stroke stops when it runs out. On release, a deterministic path evaluator checks the line: it must connect both sides, stay under the slope limit and avoid rocks. The car then drives the drawn path. A win ends in LEVEL CLEAR; a steep segment stalls the car, a rock crashes it, and a short line never leaves the start.
Test whether a single stroke can carry a puzzle, and whether distinct fail presentations (stall, crash, disconnect) teach the rule without text.