Know how a camera lens has blades that glide over eachother to adjust the diameter of the orifice allowing light to pass through [needs better grammar]? How about we reverse that and fasten blades to a center point, such that them gliding across eachother adjusts the total diameter of the assembly? That would net us a cup lid with a continuously variable diameter. Lost a regular cup lid? Not to worry! Got a cup but no fitting lid? Not to worry! Licenced as CERN-OHL-S-V2 https://ohwr.org/cern_ohl_s_v2.pdf