The teacher draws ten points round a circle on the board and joins each point n to point 2n mod 10, showing how few chords that gives. Students then open a p5.js starter sketch that places N points on a circle, and write the loop that joins each point n to point k × n mod N, with sliders for k and N. With N = 200 they find that k = 2 gives a cardioid and k = 3 a nephroid, look for the rule linking k to the number of cusps (k − 1), and then extend the sketch in their own direction, such as colouring chords by length or animating k through decimals. Over two lessons they finish the sketch and post it to a class Padlet wall with a 100-word statement explaining the modular rule and the cusp pattern.
Tools: p5.js, Padlet Nine ideas for your own version in Generate
This page is one of a growing set of PICRAT examples by cell, subject and grade. Page maintained by Andy Perryer.