A Light in the Dark
A Light in the Dark is a level in Yoshi's Island DS. It is similar to Super Mario World's Tubular. This is by far the most difficult level in the game, even moreso than Yoshi's Island Easter Eggs.
In this level, the player start off in a castle where the goal is to find two keys to unlock two doors. It is very easy to lose a life here due to all of the spikes and purple skies throughout the level. The entire level is lit by torches. Once the player gets the keys, he then goes outside onto a mountaintop at night illuminated by torches. He then has to complete a skiing section which involves instantaneous decisions and perfect timing.
Once that is completed, the player has to get past a small maze section with spikes which is throughout populated by crabs. There is a small Superstar Mario section right before the goal followed by use of the smiling platforms which are affected by the player standing on them.