A wall can turn a basic core session into something much tougher.
This sequence changes the angle and movement pattern each time, so your abs, obliques and hip flexors have to keep adjusting instead of repeating the same crunch over and over.
Control the reps, keep your lower back steady, and let the core do the work.
This is why masculinity is good. It creates boys/men who are emotionally regulated. All the male criminals you see in the world can't regulate themselves.