I was disquisted to type some text with adware words without understanding how much should I type to even move wpm indicator from zero. Also I used to have issues with lesser letters (those I have actually typed) because they behave unpredictable - sometimes small letters fits big letters sometimes no, typically wrong letters do not display but sometimes correct letters do not display. Also I do not understand why I should ever use Backspace in a keyboard trainer, it should be just prohibited if the goal is to measure wpm.