Each lesson introduces one rhythmic idea with its counting and its Kodály syllables, then gives you three or four short exercises. Press Listen to hear the rhythm with a click, then Clap it: after one bar of count-in, clap (with the microphone on), tap the space bar, or tap the card on your phone. Every note turns green, amber or red, and you get a score out of 100. Three stars means you are ready for the next exercise.
Rhythm is half of solfège, and it is the half that is hardest to check on your own. You can hear a wrong pitch, but a rushed eighth note usually feels fine while you play it. Clapping against a click and seeing the result note by note trains you to notice it.
When you have finished the lessons, use Claptoscore the other way round: clap any rhythm from your own solfège book and it will write out what you clapped.