TUTORIAL: Building games in Flash 5
Part 1: Player movement and fire.

Author: David Doull
Date: 23/02/01
Download source files: tut1.zip

Lastly the moveSpeed bit. Remember we set moveSpeed equal to a fixed value of 10 earlier. So if the left arrow was pressed the x-position would be set to the previous x-position -10 (ie: ten is subtracted from the previous x-position).

If the right arrow key is being pressed then the new x-position is the previous x-position plus 10.

so the code:

if (Key.isDown(Key.RIGHT)) { 

  this._x+=moveSpeed; 
} 

else if (Key.isDown(Key.LEFT)) { 

  this._x-=moveSpeed; 
}

means: " if the right arrow key is being pressed down then increase the x-position of the current movie clip (the spaceship) by the value of MoveSpeed (which is 10),
Otherwise if the left arrow key is beign pressed down then decreasse the x-position of the current movie clip (the spaceship) by the value of MoveSpeed (which is 10) "

Finally, the code:

if (Key.isDown(Key.DOWN)) { 
  this._y+=moveSpeed; 
} else if (Key.isDown(Key.UP)) { 
  this._y-=moveSpeed; 
} 

does the same thing only it increases or decreases the y-position of the spaceship based on the UP or DOWN arrow keys.

If you want to skip all the above typing you can download the following fla: tutorial1_part1b.fla

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