How it works
A word made only of the home row letters a, s, d, f, j, k and l never makes a finger leave home.
Dad, ask, lad, sad, all, fall, salad and flask are home row words.
Slow and right beats fast, so look at the screen and not at your hands.
If a key is off, use backspace to rub it out and fix it. Fixing a slip is part of typing.