As the title mentioned. I'm puzzled when the quiz shows nothing but the onyomi without any additional context such as jukugo or meanings. Already tinkered some quiz options but got stuck :(
I like this vector for writing practice. For kanji with very common onyomi you can just draw and select any kanji with that reading you can think of and if it's not the correct one for this question, you get an option to see the meaning as hint. Use that, because if you continue to randomly choose another kanji with the same reading, the question will be counted as wrong. For 2 or more kanji with the same readings and very similar meanings it can happen that you still write the wrong kanji for the question. In that case it will switch to multiple choice.