An invisible object is in orbit around your screen. Click where you believe the object should be and it will appear briefly, confirming whether you hit or miss and potentially betraying its speed and orbit radius. You cannot click during this period of visibility.
The score, a simple count of hits and misses, is kept in the lower-right corner.
Every fifteen seconds, the center, radius, and speed of orbit changes randomly. The time until the next change should probably get dropped into the scoreboard or the change signaled somehow, but that's not the case at this time. The timer is also hard-coded at this time, though can easily be scaled to the user's skill or randomized.
This file is authored in Markdown. Use the
convert.sh script (assuming that Pandoc has been installed) to translate it into HTML. This creates
readme.html, which is loaded and displayed by the game's About button.
Unless you have installed this, though, you probably already know that last part about the About button, since you probably just clicked it. Odds are also that you don't care, in that case.