Produces an orderly sequence of numbers, no one to know exactly where it starts or stops in future...
Each bang elicits the next number in the sequence from 'start' to 'done'.
When it reaches 'done,' both start and done step closer to sdest and ddest, respectively. The sequence resumes somewhere between the new start & done.
When sdest or ddest are reached by this progression, a new sdest or ddest is planted randomly between 'bottom' and 'top'.
inlet 2: move 'start' to this number and restart.
inlet 3: move 'done' to this number and restart.