First, the header. Two irrelevant lines (probably a sort of magic string).
Next, there's the description. Finally, you have 64 lines for every color in the colorset in a scalar RGBA format.
Then, the actual bricks. This section starts with "Linecount" and then the total number of bricks.
From then on, every brick is represented as a line.
Bricks can have additional properties such as events or items which are placed right after the line and are formatted like "+-OWNER 20000".