I've been learning Mandarin for about 3 years now. In April 2017 I released my own program to add spaces between words: https://pingtype.github.io

The best spaced repetition method for me is listening to music. If I watch a film 5x or see a flashcard 5x or read a comic 5x, I'm bored. But I can listen to the same song 20x and still like it.