Reps-based HIIT workouts for travel?

Hey everyone,

I am going on a summer camp soon and I want to do some bodyweight workouts. We won't be allowed to use our phones so I figured I would write a few workouts down or print them. I am looking for repetition-based HIIT cardio workouts around 20-30 min that I can do without a phone/timer by just counting the reps. I would greatly appreciate any suggestions. Thank you all and have a wonderful day :D