A hollow red circle emoji, often used to represent emptiness or nothingness.
Unicode: U+2B55
The hollow red circle emoji (⭕) is a simple yet versatile symbol that can convey a range of meanings, from representing a zero or nothing to indicating a lack of something or a void. It is also commonly used in games, puzzles, and diagrams.
I have ⭕ energy left after that long workday.
The instructions said to mark the starting point with a ⭕.
In the game, you have to collect all the ⭕s before moving to the next level.