If you have ever played Galaga then this game will seem fairly similar. Use the left and right arrows to control the ship at the bottom and use the space bar to fire octopus projectiles at the bombarding ghosts. When the octopus is fired it will move slowly while it charges for a split second and then take off. The octopus will only destroy ghosts once it has charged so make sure it has room when you fire it. See how long you can survive and rack up your score!
To make this program I just had to make 5 sprites. The ship, three enemy ghosts and an octopus projectile. The ship uses a deceleration when you release the arrow key so that it doesn't come to an immediate stop. I got that idea from another scratch project that I found when I was looking into applying some sort of gravity, but I was unable to find the project again when I was looking to cite it. Ghost 2 is the only one that attacks every time. The other two attack at a probability that increases as the score gets higher so that when you are at over 500 points it is very common for all three ghosts to be attacking you at once.