The hundredth thing you build is faster than the first — hands learn. Every time cumulative output doubles, the time per unit falls by a fixed fraction. Slide how fast the crew learns, tap to build another unit, drag along the curve to leap ahead, and watch the cost fall.
Wright's law (1936): unit time T(n) = T₁·n^b, where b = log₂(learning rate) — an 85% curve means each doubling of cumulative units cuts unit time to 85%. Slide the rate, and the exponent, the time for the nth unit, the cumulative average, and the total labour (Σ T(i)) all recompute exactly. Build units one at a time or leap along the curve by dragging; the cost per unit visibly falls with experience. Real, measured manufacturing learning-curve mathematics.
A single smooth exponent stands in for real learning, which plateaus, resets when the line or crew changes, and mixes with automation and scale effects. The curve T₁·n^b and everything derived from it are computed exactly; that a fixed percentage holds forever is the idealisation.