Basic Asteroids clone written in Scratch
Scratch provide a library of sprites and backgrounds that you are free to use.
The Spaceship is the obvious choice but you are free to pick whatever you like. Scratch also provides a basic Rock sprite which we can use to represent the asteroids.
Click on the spaceship sprite in the Sprites window that is under the playing area.
Click Scripts window.
You will see a list of categories - Motion, Looks, Events, Control and many others.
Click on Events.
Add the code that will resize the sprite when the game starts.