Play it cool.
Play it cool.
Play it cool" means to stay calm, not overly excited, and behave nonchalantly in a situation where showing too much excitement or anxiety could be a disadvantage. It’s like acting cool under pressure.
Just play it cool when the boss asks about the project.
Stay calm when the boss asks about the project.
Even if you're nervous, play it cool.
Even if you're nervous, remain calm and composed.
When she walks in, just play it cool and act like you're not interested.
When she enters, act indifferent and composed.