How many random draws to collect all n distinct coupons? Draw by hand, then run thousands of simulations and watch the empirical mean lock onto the theory E[T] = n·Hₙ.
Each cell is a coupon; the number below is how many copies you have drawn.
The curve shoots up early, then flattens: collecting the last one or two coupons eats an enormous number of draws — the "gacha completion" problem made visible.