Picolarium is a PICO-8 clone of the game Polarium for DS.
Draw a single stroke, flip tiles from black to white or vice versa, and turn each single line into a solid color each.
There are 100 levels, and each level has a hint if you're stumped.
The game contains a level editor, which lets you create your own levels (20 can be saved at a time) and share them with others through 30-digit passwords (compatible with Polarium and Polarium Advance).
You can also input passwords to play other people's custom levels. There are some custom levels online you can challenge yourself with:
Play Picolarium here: