Always use your map! It's the most helpful tool in the game. Here is the map key:

Moving Green Dot - You

Stationary Green Dot - Exit

Red Dot - Grundo

Brown Dot - Unsearched Crate

Blue Dot - Searched Crate

TIP: Running does not decrease your time any faster, so run as much as possible. Be careful, though, running also attracts Grundos.

TIP: There is more than one plushie on each level, so don't worry about the time limit unless you haven't found the plushie when you have 1/4 of your time left.

TIP: The Nova at the bottem of the screen pulsates faster as you approach a Grundo.