Not going to give the question. Had to use mostly vanilla javascript including; setInterval, Math.floor, Array.slice, % operator and understand global vs function vs block scope. Bonus points for understanding request animation frame, this, and the event loop. If you get stuck explain to the engineer your solutions and why they dont work and ask for a hint. I had 2 hints and got the offer. The interviewer obviously knows the solution so dont try and outsmart them. Goodluck