For the first 20 keys or so, only add 2 keys at a time to a new level. Let the user practice the keys alone first in different combinations and then use the new keys in words and mixed with already known words.
Per a les 20 primeres tecles, afegiu tan sols 2 tecles alhora a un nou nivell. Deixeu a l' usuari practicar a soles en diferents combinacions i aleshores useu les noves tecles en paraules que podreu barrejar amb les ja conegudes.