ao is a captivating game available on iPhone that belongs to the "focus" series developed by General Adaptive Apps Pty Ltd. In this game, players are presented with an expanding and contracting circle with different radiuses. As you progress through each level, the circle changes, offering theoretically infinite ways to complete each level.

With 200 levels to solve, ao keeps players engaged with various tweaks and surprises. The game also features a leaderboard where players can compete for medals, including bronze, silver, and gold. Additionally, players have the option to go back and replay any level they've already passed, providing flexibility and the opportunity to improve their performance.

For those facing challenges on a particularly difficult level, there is a skip option available on the Fail Screen. Furthermore, players can unlock all 200 levels to replay at their own pace by choosing the "Unlock All Levels" option.

Overall, ao offers a unique and enjoyable gaming experience with its expanding and contracting circle concept. It is a free game that provides hours of entertainment and is a great addition to the "focus" series.