Challenges: (ranked roughly from easiest to hardest)
 -  put user in a python shell, have them try to read the flag from a file
 -  2l.sh - read flag from a file using only 2-letter shell commands
 -  approved.pl - read flag from file using only the commands ls, pwd, whoami
 -  patience.c - find the code from a binary executable that will print the solution in 1 year's time

Make sure there is a different flag for each challenge.