No gym, just core

So today my gym buddy had an appointment early in the morning so we could meet at the gym earlier. Unfortunately, i went to bed really late last night and i also did leg day, so i was very tired and i couldn't get up. I decided to just get up when i wanted to and make sure that i was ready to get at least before 2 PM. Then when i checked my messages, my gym buddy cancelled our gym appointment. So if i had gotten up earlier we would've been to the gym. Eh. My own fault. I think i will instead just do some core routine. I don't know what i will do yet, but i'll figure it out. Every time i try to find information about what people with good bodies do for core they all claim that they don't do anything special, but i know they do. Why is everyone so secretive about it lol.