import time
indent = 0 # How many spaces to indent.
indentIncreasing = True # Whether the indentation is increasing or not.
while True: # The main program loop.
    print(' ' * indent, end='')
    print('********')
    time.sleep(0.1) # Pause for 1/10 of a second.
    if indentIncreasing:
        # Increase the number of spaces:
        indent = indent + 1
        if indent == 20:
            # Change direction:
            indentIncreasing = False
    else:
        # Decrease the number of spaces:
        indent = indent - 1
        if indent == 0:
            # Change direction:
            indentIncreasing = True