This appears to be a case of a costume interfering with a slider. Use the Space key to change the costume of the "ground" sprite. Costumes 1 and 2 appear to block the slider (does not respond to mouse) while costume 3 does not. All the costumes appear the same - I noticed that the dimensional height of the original costume (costume 1) was reported as larger than it visually appeared so I used the paint editor to delete invisible pixels above the tops of the trees resulting in costume 2 and finally costume 3. I could not find the stray pixels through my usual method of filling the empty space with a bright color (red or yellow) and looking for "holes" Other information...removing any one of the three remaining sprites allows the slider to move. Removing the "Go to Front" blocks on the Ground and Alarm sprites allows the slider to move.
