Checkmarks, colours, and time estimates

On a subject's page:

• Read segments turn green with a check. Finished lessons get a green row, and finished topics a green badge.
• Each topic shows how many of its segments you've read.
• Every segment, lesson, and topic shows its estimated time, or time left once you've started.
• At the top: estimated time left for the whole subject, and the real time you've spent on it.

Mark things complete yourself: tick the circle next to a segment, or use Mark lesson complete to finish a lesson without its quiz.