Coin-Like Die

Roll a die with a 50/50 chance, like a coin. One of the sides has a star, which can mean something in your game.

In one of my RPG, stats are given from 1 (okay) to 4 (amazing expert) with difficulties ranging from 1 (normal challenge) to 4 (impossible). To accomplish a task, roll the number of these coin-like dice equal to your stat, and if you get a number of successes equal or exceeding the challenge, the task is successful.

Simple and doesn't require much mathematics.