The item texts and tab titles use HTML code. So the appearence can be anything HTML can express. Font-sizes, colors, images, links and multi-line are supported, to name a few.
Unlimited number of tabs. Tabs have different background colors.
Items are organized in arbitrary levels. Sub-items can be folded.
Sub-items and their parents are logically related. The parent is marked as finished if and only if its children are finished. The finish time of the parent is the latest finish time over its children.
Data can be exported as a JSON format file. So you can store it into a text file, and import somewhere else.
Simple text format also makes modify the data by your own. Exporting, modifying and importing again.
Local Data Storage
All data are stored locally using HTML 5. The mostly recommended browser is Chome.