Help! I can't remember the code! Year 3-4

Help! I can't remember the code! on PhotoPeach
This was a rich acivity for reading and writing numbers up to 1000.  Lots of discussion took place related to Place value....what is the value of the 0.  Can it be at the beginning of the number...how much is it worth in the middle/end of the number?  If the code is between 500 and 800 could it be 450?  If the number onely has one zero....could it be 600?  Look for the clever number patterns we created as we tried to solve this problem!