ao is a free strategy game developed by General Adaptive Apps Pty Ltd for Android devices. It is the 6th game in the "focus" series, which includes aa, uu, ff, au, rr, rl, sp, and th. The game features an expanding and contracting circle with different radiuses, and the objective is to complete each of the 175 levels by finding the theoretically infinite ways to finish them.

As you progress through the levels, the game changes, making it more challenging and fun. Additionally, you can top the leaderboard and earn medals, including bronze, silver, and gold. You can also replay any level you have already passed or skip a tricky level by tapping on the Fail Screen. If you cannot wait, you can unlock all 175 levels and play at your own pace by selecting Choose Level and then Unlock All Levels.

Overall, ao is an entertaining and challenging strategy game that will keep you engaged for hours. It is handmade in Australia by General Adaptive Apps Pty Ltd.