The classic press-up — push your bodyweight away from the floor. Drop to your knees to start; that's the right version, not a lesser one.
Every move in Core Buddy has a video like this one — and it builds the whole session for you, timer and all. Free to download.
The same press-up from your knees. It builds the same strength, and it counts just the same. Work with this version for as long as you like — when the full one feels within reach, give it a go.