999SLTenebris is a pulse-timing tap game built around a circle that repeatedly expands and shrinks. Tap only at the maximum outline instant to score. Other taps count as mistakes, and three mistakes end the run. Cycles speed up as your score rises, shrinking the safe window. Early or late taps both spend the error budget under rising tempo. There is no second-chance linger at peak size. Clear outline scaling makes the max moment readable when you stay focused. Simple tap-at-peak rules with a three-mistake fail. Great for precision timing, escalating cycle speed, and retry-friendly scoring.