You steer and you hold boost. That is the entire control scheme. The highway decides everything else, and it decides it from a short string you can hand to somebody else so they drive the road you drove.
A and D, or the arrow keys, move the ship across the road. On a phone, drag anywhere to steer. There is no brake, so the only question is which side of the next block you want to be on.
W, Shift or the up arrow buys half as much speed again and twice the score rate for as long as the meter lasts. A second finger does it on a phone. Orbs refill the meter, so a clean line pays for the next one.
Going past a hazard with under a metre and a half to spare is a near miss. It pays 250 points times your combo and raises the combo, to a maximum of ten. Five safe seconds and the combo drops a step.
A crash ends the run and offers a link carrying the seed and your score. Whoever opens it drives the identical highway with your number on the screen until they pass it.
The seed
The track, the hazard patterns, the towers and pylons along it and the colour of every level all come out of one string. Hand that string to someone and they drive your road, block for block. There is a daily one as well, named after the date, the same for everybody who opens it.
The curve
Every 650 metres the speed goes up, the road narrows, the gaps close and the sweeping blocks move faster. The curve approaches a limit rather than reaching one, so nothing on the road is unsurvivable on paper. It is only unsurvivable by you.
Overdrive runs in a browser tab, free, and there is nothing in it to buy.
No account, no advertising, nothing for sale, and no network request once the page has loaded. Your best score, your best on each seed and how many runs you have had sit in the browser you played in and go no further. There is no last level to reach: the highway keeps going, and you stop when you hit something.