Let's talk about how it was made!

The Scene

This nebulous and slightly-swirly background was added to the room to give it some outer space vibes!

The Spaceship

The spaceship's direction variable changes if the left key or right key is pressed.
The image_angle variable is set to the direction variable so the sprite of the ship will point to the direction its facing.
The spaceship's speed variable increases as long as the player is holding down spacebar. We limit the speed of the spaceship using a clamp() function so it doesn't go too fast!
When the ship's speed variable is 0, its image_index variable is set to 0 so the thrusters don't animate.
The spaceship's friction variable automatically decreases the speed variable when spacebar isn't being held.
If the spaceship leaves the room's bounds, we change its x and y values to the other side of the screen.

A controller object controls when and where the stars appear.
An instance of obj_effect_sparkle has a 1-in-50 chance of appearing every step at a random position in the room.
We used Multi-colored effects to create twinkling stars with different colors using only one sprite.
In the star's Animation End event, we have it destroy itself.

The planet is made up of three objects! The body and face are one, and there's one object for each ring of haze around the planet!
Each step, the image_index variable increases at different speeds for each ring of haze.
Each layer of haze has its image_alpha variable set to .2 to make it transparent.
In the body object, the face is drawn starting at the center of the planet, then offset in the direction of the spaceship using lengthdir_x() and lengthdir_y(), but not so far as to move off of the body of the planet!