cerebral
Related to deep thinking or the brain, not emotions.
Cerebral means relating to the brain or intellect, and it's often used to describe things that require serious thinking rather than physical action or emotion. A cerebral movie might have a complex plot that makes you think hard about its meaning, while a cerebral person tends to approach problems through careful reasoning rather than gut feelings.
When someone calls a book or game cerebral, they usually mean it challenges your mind. Chess is a cerebral game because success depends entirely on strategic thinking. A cerebral conversation explores deep ideas rather than small talk about the weather.
Scientists use cerebral in medical terms like cerebral cortex, but outside of medicine, it's often a compliment about intellectual depth. If your teacher says your essay was cerebral, she's praising how thoughtfully you analyzed the topic.
Calling something cerebral can sometimes suggest it's overly intellectual or hard to connect with emotionally. A cerebral approach to friendship might mean someone analyzes everything but forgets to enjoy being together.