from Astrachan, pp 100-101.
------------------------

prompt> fly
Welcome to the windbag emporium.
You'll rise up, cruise a while, then descend.
How high (in meters) do you want to rise: 20
How long (in seconds) do you want to cruise: 10

***** (Height = 0) Ascending to 20 meters *****

0 meters  Burn!
10 meters  Burn!

***** Cruising at 20 meters 
***** with margin +/- 5
****  for 10 time-steps

20 meters (time step 0) 
20 meters (time step 1) wind-shear -3 m.
17 meters (time step 2) 
17 meters (time step 3) wind-shear -4 m. too low!  Burn!
23 meters (time step 4) 
23 meters (time step 5) 
23 meters (time step 6) 
23 meters (time step 7) wind-shear +3 m. too high!  Woosh!
16 meters (time step 8) wind-shear +1 m.
17 meters (time step 9) 

***** (Height = 17) Descending to 0 meters *****

17 meters  Woosh!
7 meters  Woosh!

prompt> fly
Welcome to the windbag emporium.
You'll rise up, cruise a while, then descend.
How high (in meters) do you want to rise: 20
How long (in seconds) do you want to cruise: 10

***** (Height = 0) Ascending to 20 meters *****

0 meters  Burn!
10 meters  Burn!

***** Cruising at 20 meters 
***** with margin +/- 5
****  for 10 time-steps

20 meters (time step 0) 
20 meters (time step 1) 
20 meters (time step 2) 
20 meters (time step 3) wind-shear -3 m.
17 meters (time step 4) wind-shear -1 m.
16 meters (time step 5) wind-shear -3 m. too low!  Burn!
23 meters (time step 6) wind-shear +5 m. too high!  Woosh!
18 meters (time step 7) 
18 meters (time step 8) wind-shear +5 m.
23 meters (time step 9) 

***** (Height = 23) Descending to 0 meters *****

23 meters  Woosh!
13 meters  Woosh!
3 meters  Woosh!