There are two game modes: Solo and Multiplayer, both of which can be accessed from the start screen. On several screens, there is an X cross in the upper right corner. Tapping it brings you back to the start screen. The trophy in the upper right corner of the start screen brings you to the highscore.
The menu  in the upper left corner leads you to further information about the game:

• Feedback: Feedback about particular questions or anything else regarding this app is very welcome. You can enter it in the web form.
• Submit your question: Currently there are more than 700 questions in the library. If you want to suggest your own quantum-related question, please submit it via the web form opening when you press this menu item. Do not forget the three wrong answers, they are as important as the correct one. A reference or link that proves the correct answer in the comments field is appreciated.
• Tell a friend: This is an easy way to notify others about the Quantum Quiz directly from your smartphone using your favorite messaging app, e-mail or social media app.
• Imprint: Should be pretty evident.
• Privacy Policy: The name says it all. Note that we have no interest in using this app to collect any of your personal information for anything else than what is essential for the quantum quiz to work.

At the start of the game and in between questions, tap anywhere on the screen to continue.

Any interruption of the app will restart the game to prevent cheating attempts. The game will either end after 9 questions of when you have lost both lives.

You then have the possibility to add your result to the highscore.
There, you can tap Share your score to share your result via your favorite social media app, via a messenger app or via e-mail.

Up to 4 people can play in each multiplayer game. Several parallel multiplayer games are possible. First, you have to choose a room key, which can be any combination of numbers and characters and is case sensitive. The app will notify you if a room of the same name is already occupied. The person who opened the room (i.e. entered it first) has a special status. Only this person can start the game by pressing Go at any time after at least a second player joined; and only this person can initiate display of the next question by tapping anywhere on the screen once everybody’s pick was displayed.

Everybody’s pick will be displayed with a unique identifier consisting of the first two characters of the player’s name and a number from 1 to 4. Do not worry if the timer in the upper half of the screen keeps running even though you have already selected an answer. The app will only count the time from the moment the question was first shown to when you tapped your answer.

The game will either end after 9 questions of when all players have lost their lives. If a player loses their life, they can continue to play, but only the questions answered correctly before they lost their second live will count towards the highscore. This fact is indicated by a semitransparent name tag. Once the game ended, a ranking of this multiplayer game is displayed. Every player has the opportunity to add their individual result to the highscore. There, you can tap Share your score to share your result via your favorite social media app, via a messenger app or via e-mail.

When pressing New game or exiting the highscore after a multiplayer game, the old room key is already filled in. Just tap Go to start another round.