Make a monster that is impossible to pass

In a platform activity, you can make a monster mimic the character along the x (horizontal) axis and make it impossible for a character to get past.

Within a platform activity select a "monster" and place it either above or below your character. Right click on it then click on the green rotation arrow below the image to view the animation options that are attached to the monster. Click on the red fish (for animation settings) and click on the "adv" option. in the script box that appears, enter the following code;

this._x=_root.player._x;

Now everytime you move to the left or right, the monster will move exactly the same distance either above or below you.

View example; Download Impassable