The term "no-brainer" is used to describe a situation or decision that requires little effort or thought. However, there are several synonyms for the word "brainer" that can be used to convey different levels of simplicity or complexity. For instance, the words "obvious," "clear-cut," and "straightforward" can be used to describe a situation that requires little thought or effort to understand. Conversely, words such as "challenging," "difficult," and "complex" can be used to describe situations that require significant effort or expertise to solve. Additionally, words such as "intellectual," "genius," and "brainy" can be used to describe individuals who possess exceptional intelligence or problem-solving abilities.