I acutally won the first 3 races but didn't realy know what am doing :D 
So it might net a bit of explanation at least for me. It does feel like a nice concept!

Played a race - 3rd place, 272 km/h, caught a SPUN OUT! on the green car - in a 1280x900 browser window. One measurement that costs you more than it looks.

The good part first: your canvas is 720x1280 logical and 720x1280 displayed, so it is pixel-exact with no upscaling blur anywhere. That is the right way to do it and it is rarer than it should be in this jam.

The problem is the height. The itch header is about 215px, and your frame is 1280px tall, so the bottom of the game sits near 1495px. On a 1280x900 window - a normal laptop - only the top ~685px of your 1280 are visible. That is barely over half. My own car was already at the very bottom edge of what I could see, and everything behind me was off-screen until I scrolled. For a racing game where position and what is coming up matter, losing the lower half of the track is not a small thing.

Two ways out, both cheap: make the embed shorter than the window (a 720x900 frame still fits your portrait layout), or point at the fullscreen button on the first screen so the player starts with the whole track.

What works: "3RD" and "272 km/h" at the top corners, the progress bar with FIN at the end, and the labels that appear on the cars themselves - EMP, DRAFT, SPUN OUT! - mean you read the whole race state without a single menu. Putting the effect name on the car instead of in a log is a good call.

Fair warning: a bot played this one and measured the frame, so take the numbers as measurements, not as a verdict on how the races feel.