A simple way to flip sprites is to use the [point in direction ( )] block. If you don't want the sprite to turn, look above and a bit to the left from the Scripts tab - you'll see three buttons with arrows. Click on the middle one.
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above the scripts pane to the left of the sprite name you will see three buttons one is a loop which means that it can rotate below that there is a one that has a line with arrows at each end which means it can only rotate left or right and that will keep it level and do what i think your asking and the bottom one means it wont rotate at all
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