''' Purpose: deepen variable manipulation understanding.

    Problem: track the number of rabbits over five generations, where
             the number of rabbits doubles each generation. at the start
             there are two rabbits
'''

# first generation
generation  = 1
nbr_rabbits = 2

print( 'Generation: ', generation  )
print( 'Rabbits:    ', nbr_rabbits )

reply = input( 'Enter when ready: ' )           # waits until user enters something

# next generation
generation  = generation + 1    # Increment generation by 1 = 1 + 1 =       2
nbr_rabbits = nbr_rabbits * 2   # Double the number of rabbits = 2 * 2 =    4

# variable = variable + 1
# says reassign variable to the LAST value of variable + 1
# So the LAST value of generation was 1
# so generation is assigned 1 + 1 = 2

# nbr_rabbits = nbr_rabbits * 2
# nbr_rabbits = 2 * 2 = 4

print( 'Generation: ', generation  )
print( 'Rabbits:    ', nbr_rabbits )

reply = input( 'Enter when ready: ' )           # waits until user enters something

# next generation
generation  = generation + 1    # Now generation is 2 so 2 + 1 =    3
nbr_rabbits = nbr_rabbits * 2   # Now nbr_rabbits is 4 so 4 * 2 =   8

print( 'Generation: ', generation  )
print( 'Rabbits:    ', nbr_rabbits )

reply = input( 'Enter when ready: ' )           # waits until user enters something

# next generation
generation  = generation + 1    # generation is 3 so 3 + 1 =    4
nbr_rabbits = nbr_rabbits * 2   # nbr_rabbits is 8 so 8 * 2 =   16

print( 'Generation: ', generation  )
print( 'Rabbits:    ', nbr_rabbits )

reply = input( 'Enter when ready: ' )           # waits until user enters something

# next generation
generation  = generation + 1    # generation is 4 so 4 + 1 =    5
nbr_rabbits = nbr_rabbits * 2   # nbr_rabbits is 16 so 16 * 2 = 32

print( 'Generation: ', generation  )
print( 'Rabbits:    ', nbr_rabbits )

# We want to update the values of generation and nbr_rabbits each time!
# variable = value
# left side gets assigned to the evaluated right side
# When we have a new variable, there's a memory box (in your computer memory)
# to store the value for that variable.
# If we reassign the variable, the value in that box for that variable changes!