You'll have to excuse me, I'm a little out of it. After a few short sessions with Entwined Challenge, going back to a boring writing window is kind of like dunking your head in ice water. This abstract casual game comes from developer Pixelopus, the maker of the full Entwined game on the PS4, PS3, and PS Vita. Now you can get a bite-sized version of the experience on your Android device, Sony or not, in the Play Store. Entwined Challenge is $1 with no in-app purchases.
In Entwined, you control one character with either thumb: an orange fish on the left and a blue bird on the right. Both are constantly moving down a circular tunnel, and you control their positions by sliding up and down on either side of the screen. The mechanics are simple, just line up the fish and bird with the glowing petal-like things as you zoom down the endless level. But the atmosphere created by the abstract visuals and music is nothing short of hypnotic - it's a truly "zen" experience. It reminds me of SEGA's Rez, though Entwined is much calmer and simpler.
Here's a video of the original Entwined. The Android version of the game contains only the Challenge mode, and the graphics aren't as fluid or detailed, but you can get a good idea of the gameplay from the video.
Entwined Challenge contains five levels, though they're all very similar - it's essentially a theme change in each one. Unlockable concept art will give you something to strive for if online leaderboards aren't enough.