Tip: When determining a time limit, remember that players won't be as familiar with the level as you are. If you normally complete the level with the timer around 100, others might run out of time on their first try.
This is my level that I've almost finished. The gimmick is that Mario (or Luigi) traverses the same area at least twice: both during the day and during the night. At night, everything freezes over (hence the level name). Turn blocks and block bridges freeze solid; water becomes deadly cold; the ground freezes and expands in a few places; everything is slippery. In order to get the normal exit, you need to play through the area at least twice to get the necessary item (there's a little shortcut so you don't need to go through a third time.) I've uploaded an IPS patch, so some feedback before I submit the final file would be nice.