• Tap left or right to match the next stair direction and climb endlessly.
• Miss a direction or let the time bar hit zero and you’ll tumble down.
• Pace tightens as the drain accelerates; keep rhythm to push your best.
• Clean light‑mode canvas, subtle animations, pause and sound/haptics, autosave best.
• Single‑file HTML/CSS/JS in a fixed 500×800 mobile frame.

---