The brain ... just like any other muscle in the human body; needs stimulation.. like sharpening a tool, if you may.
Puzzles, (e.g. crosswords) and creative games that creativity & ingenuity; helps a lot in keeping those brain cells alive & well.
The basic squat is also a good core exercise.
Mix in a kettlebell... let's you do a goblet squat.
Good for:
Glutes
Core strength
Knee strength
Mobility