In 'TotallyNotSpaceInvaders', the player controls a ship that appears at the bottom of the screen.

The player can move the ship right and left using the arrow keys and shoot bullets using the spacebar.

When the game begins, a fleet of aliens fills the screen and moves across and down the screen.

The player shooots and destroys the aliens.

If the player defeats all the aliens, then a new fleet appears and moves faster than the previous.

If any alien reaches the bottom or touches the player's ship, a life is lost.

If the player loses three ships, the game ends.