This may be the most pure video game I've ever played. It doesn't get any simpler than Sinius. Avoid the red dots, pick up the blue dots. That's it.
Sinius also has an amazing soundtrack. The kind I don't mind leaving on in the browser as I work. It's also dynamic - pick up a power up and the drums kick in that little bit harder, die? The music retreats into single, sombre chords.
Simple, basic and charming.