I've been using Uberchord for a few years by now and it's just amazing. It's all about chords, rhythm and songs. This is no child's game, though, you actually learn how to play. The recognition works for most of my guitars and is borderline crazy, even showing me if I put a finger on the wrong fret. It won't let you just play anything and still pass. They have courses library (they call it learning path) and a pretty large catalog of popular songs. I wish they had solo training, but all in all, highly recommended.
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