Before I mention anything else, you need to have the start screen not be only usable with a tap of the mouse, and that start screen for the level shouldn't pause the game and more so be something over the start of the level. Since it's keyboard controls only (outside of the mobile controls built in), and then asking the mouse every time when resetting is a little annoying. Please allow the spacebar to work with it if you plan on having a web/PC version outside of mobile in the future. It's one thing you really have to change the most. It's the only main negative I have as well.
The graphics are really good, very professional. Reminds me a lot of Happy Wheels and the gameplay is very fun. Backgrounds work perfectly with the theme of a car testing facility. Every graphic for the UI and menus are very well made too. You made a very well made game.