I remember watching Jim Bathurst ages ago doing 90 degree Push-ups. It was this video (he also dips lower than normal, which is pretty cool). Man that guy is an inspiration: It's a rather rare skill, but some others have worked on them. LittlebeastM comes to mind in particular for getting a ridiculous 10 in a row O_0: It's a hybrid between Planche Push-ups and HSPUs (so-called Multi-plane Pressing). Those skills felt solid to me so decided to just try one for the first time today: I was happy to get one and humbly wanted to share with everybody I'm super excited to add it to my training now. It really feels like a unique and worthwhile skill. No wonder so many people have recommended me to work on them haha. Keep on rocking on fellow BW trainees!