Fun to play, but with some issues to work on (for the future).
1. Only local multiplayer is a bit boring, at least for testing.
2. But the full game, with local multiplayer, is fun, so it could be part of a racing game without (only) multiplayer.
3. I didn't notice any sense of urgency. A lap counter and a timer could help.
4. The lap-by-lap construction system is a bit clunky. I mean, at this frequency, the game is a bit clunky. I'd prefer to place obstacles and play for 3 laps against a friend (for example).
5. The car control system is good to play, but it needs some kind of adjustment, as it often oversteers the car. If this doesn't turn into a car customization system (a store, upgrades, in-game level-ups...), it's a good idea to add some kind of command/menu at the beginning of the level or during the game so I can control how sensitive the movement is.
Cool game, has potential for other things. Congratulations!