There were several rounds.
After the application already next day I received an invitation for a HireVue interview. There were some questions in Russian and some questions in English, overall not very difficult.
Then within a week I got a positive feedback about the video interview, however, I did not receive an appointment for semi-final yet.
About 1-1,5 month later Mars invited me for the semi-final: group case study and interview with HR and a line manager. I don't even understand the point of the"semi-final", it was sort of like an assessment centre, but with no extended feedback afterwards and no individual case study. The rest seemed kinda similar.
HR asked the same questions as in the HireVue interview, stared at the ceiling, laughed at some of my answers. They promised to come back to me with feedback the same day, if I've made it to the final or not, however, nobody contacted me.
Overall, the process took way too long, the semi-final was redundant, I had a really bad aftertaste.