HSK 3
Tā duì zhège wèntí zhǐshì qīngtíng-diǎnshuǐ bān de tí le yīxià.
He only mentioned this issue in passing, barely scratching the surface.
HSK 7-9
Xuéxí bùnéng qīngtíng-diǎnshuǐ, yào shēnrù zuānyán.
Studying can't be done superficially; you have to dig in deeply.