Tilt your phone, move the electron (blue) and try to catch the proton (green). But watch out! You can't touch neutrons nor positrons (gray and red)!
Major game update v 2.0:
-New engine
-IAP - buy editor and hide ads
-All levels from full Hydrogen (Classic) and several new added
-Completely redesigned UI
-Sounds
-Custom maps are now stored on SD card (or mass storage if card not present)