The star buttons choose the difficulty of the relay chain you generate:

1★ — Add, subtract, multiply and divide, using positive integers only.

2★ — The numbers can be directed (negative), so watch your signs.

3★ — Includes ‘Find X%’ cards, where you work out a percentage of the running total.

4★ — Adds ‘Find 1/n’ fraction cards as well as percentages.

Whichever difficulty you pick, every chain starts from the given number and the final answer is always a whole number.