Change one letter at a time. Every step a real word.
COLDS
CORDS
CARDS
WARDS
Green = that letter is already in the right place. The dot marks the letter you swapped.
Tap a letter to aim at it, then type its replacement. Reach the bottom word to finish.
Par is the shortest route that exists. Match it and you've played it perfectly.
Par comes from a breadth-first search over 2,705 everyday words, so the shortest route never needs vocabulary you don't have. Another 11,845 uncommon words and inflections are still playable — sneak through one and you can finish under par.