Learn — the tree above the key is the shape of Morse. Tap & hold the key (or press space) to send dits and dahs. The tree lights up the path as you go. Short press = dot, long press = dash. Pause to submit.
Listen plays a random letter from your unlocked set — type what you heard.
Chart is the full table. Tap any letter to hear it.
Koch method: start with K and M; more letters unlock as you hit 85% over 12 reps. Progress is saved on this device.