Congrats on finishing your first game! It’s a great start and is fun for what it is.
To make the gameplay even more engaging, you might want to look into adding a few more player decisions. Right now, it plays a bit like a rhythm game where you just need to tap the button at the right time. Because players can launch almost immediately, the timer does not have much of an impact. Giving the player a reason to wait or weigh their options could help make the timer feel more meaningful. It would also be cool to see some differences between the three planets to make that choice feel like it matters.
Lastly, adding some simple sound effects, especially for launching and landing the rocket, would go a long way in making the game feel more immersive. In any case, I hope you continue making games :)