Important reminder: there's no double on the first roll (each player rolls one die). But from the second turn on, doubles are possible — and they're devastating.
With a double, you play 4 times the die value instead of 2. A double 3 means four movements of 3 spaces. It's like playing two turns in one.
Doubles early in the game can transform an ordinary position into a dominant one. Let's look at the most important ones.