Welcome to day 16! Close grip pull ups, close grip push ups and bodyweight squats. I took my time on the pull up reps and added in some pauses as a way to work on my grip endurance a little bit. Push ups were done on a parallette for a little variety. 3 rounds took around 20 minutes. Simple. Fast. Effective.
Pull ups and chin ups are some of the best exercises you can do for the upper body. Both train the back, arms, and core, but chin ups target the biceps harder than pull ups. The bicep doesn't only flex the elbow (close the joint angle), but it also supinates your forearm (turns your palm up). Because of this additional action, the chin up, with its palms-facing-you position, puts the bicep in a maximally contracted position, allowing you to get extra "squeeze" and recruitment of the muscle. In other words, by placing you hands in the chin up position, the biceps are put in a position that allows they to contract harder! This will result in the biceps getting more work during the chin up than the pull up. So, if you want to maximize your arm size with your current pull up routine, consider adding extra chin up volume, either by adding a few more sets on chin up days, or training it more frequently relative to your pull up.