# PLEASE CHANGE THE SPEED, FUEL, AND ALTITUDE VARIABLES TO YOUR LIKING
# you are the pilot and need to control how much fuel you burn in the
# retro rockets so that your descent speed slows to zero just as your
# altitude above the moon's surface reaches zero. If you impact the moon
# more than 5 m below the surface, or your speed on impact is
# greater than 5 m/s then you have considered to have crashed.
# else, it is considered to be a 'done' landing.
# If you run out of fuel, the spaceship will accelerate towards the moon by gravity.
# set up the initial parameters
speed = 20      # speed approaching the moon
fuel = 1500     # how much fuel is left
altitude = 100 # altitude above moon
gravity = 1 # acceleration due to gravity
burn = 0        # initial rate of burning fuel in rockets
# while ship is above the moon's surface,
# calculate flight data and take input from user
while altitude > 0:
   # calculate how long until ship will impact moon at current speed (impact)
   if speed <= 0:
       impact = 1000
   else:
       impact = altitude / speed
   # display flight data
   print('Altitude = ', altitude, 'Speed = ', speed, 'Fuel = ', fuel, 'Impact = ', impact, 'Previous burn', burn)
   burn = float(input("Enter fuel to burn (0-50)?"))
   # ensure rate of fuel burning is within rocket's capability and doesn't exceed remaining fuel
   if burn < 0:
       burn = 0
   if burn > 50:
       burn = 50
   if burn > fuel:
       burn = fuel
   #calculate new flight data
   altitude -= speed
   speed += gravity - burn/10
   fuel -= burn
# Hit moon surface
# display good landing or not
print('Altitude = ', altitude, 'Speed = ', speed, 'Fuel = ', fuel, 'Impact = ', impact, 'Previous burn', burn)
if altitude <- 5 or speed > 5:
   print("You have crashed")
else:
   print("You have landed")