Add a new easing function to the easefn library — implementation, tests, and documentation. Use this skill whenever the user wants to add, create, or implement a new easing function, curve, or interpolation method. Also trigger when the user says things like 'add easeInX', 'new easing', 'implement a spring easing', or 'I want to add a custom curve'. Even if they just name a function like 'easeInElastic' or describe a curve behavior, this skill applies.
2026-04-04