:: ATTRACTIVE BUT FORGETTABLE
:: AURALLY INTRIGUING
The basic gameplay of Osmos has you controlling an organism that can shoot pieces of itself in any direction to propel it in the opposite direction to move around, and it can absorb other motes that are smaller than yourself, denoted by being colored blue. Your goal is usually to become the largest mote on the game board, but other levels will give you various other objectives, and a variety of level types.
Playing Osmos HD reveals some of the subtleties of the gameplay concept, like how shooting pieces of yourself can be used not just to propel yourself in the opposite direction, but can be used to influence the motion of other objects, which is necessary in some levels, particularly in the Impasse levels where you'll be constantly causing other motes to react with each other to clear space.
Osmos HD's interface feels like it has been designed from the ground up for the iPad, using gestures to increase or decrease the flow of time, zoom in & out, and to open the menu, keeping the screen as free of GUI elements as possible, and focused on the graphics. A screen in the beginning recommends that you wear headphones while playing the game, and I too recommend wearing headphones while playing to properly enjoy the game's ambient soundtrack.
Osmos HD shows some real promise as one of the best audio and visual experiences on the App Store, with unique gameplay to boot when it releases on July 8th.