Spline

cubic-bezier easing editor drag the handles
curve
cubic-bezier(0.42, 0, 0.58, 1)
type
in-out
overshoot
none
at 50%
0.50
0 0.5 1 0 0.5 1 time → ↑ progress
accelerating arc length 1.41 monotonic
output (CSS value)
cubic-bezier(0.42, 0, 0.58, 1)