The felt bar holds seven letters that never run out. Below it sits a five-letter word. Swap in one bank letter to make a brand-new word — COVER takes an L and becomes LOVER, then a W makes LOWER — and keep going. No word can appear twice.
Stuck? The amber tray holds five swap letters. A swap doesn't have to make a word — drop one (or several) to bridge through a non-word and open up fresh bank words. Each swap letter can be used once, vanishes from the tray, and knocks a letter off your stack. In the daily Race to 10, fastest time to a stack of ten wins; Give up posts however many you've stacked. Blitz gives you two minutes to stack as many as you can.
Tap a letter then tap where it goes, or drag it straight onto the word.