Start in search mode.

1. Chase mode
    if motion seen:
	Turn towards motion.
	Reset chase timeout.
	while timeout--:
	    If motion seen:
		Turn towards motion.
		Reset timeout.
	    Move forward. 
	    if close enough:
		Greeting mode.
    Search mode.

2. Greeting mode
    Stop.
    Beep.
    Wait.
    Search mode.

3. Search mode
    Randomly select clockwise or counterclockwise.
    Clear distance.
    loop:
	distance++
	Turn.
	Move forward by distance.
	if close enough:
	    Stop.
	    Turn 90 degrees in a random direction.
	    Reverse a short distance.
	    Corner finding.

	if motion seen:
	    Chase mode.    

4. Corner finding
    Straighten out.
    loop:
	if motion seen:
	    Chase mode.
	randomly:
	    Search mode.
	Move forward.
	if close enough:
	    Lurking.
	
5. Lurking
    Stop.
    Turn in a random direction.
    Reverse in a circle 180 degrees.
    Straighten out.
    Reverse slightly.
    Stop.
    loop:
	Wait.
	if motion seen:
	    randomly:
		Chase mode.