> sdl_getticks64 was undefined

I used this because it was recommended by the docs, but it's somewhat recent (introduced in SDL 2.0.18, November 2021).

> now i just seea bunch of dots on a screen

The dots are other planets and moons you can travel to.

> i press thrust/downthrust and the circle disappears

If the circle disappears then you've crashed into the planet (it will blink CL in the bottom right). You'll have to start a new game, and thrust in the other direction this time. I've added some more information to the README about the gameplay.