G3T13: Light: sources, straight lines, shadows — how it looks on TimeBack

What this is. The topic in the order a student meets it — intro, each lesson, mixed practice, summary, PP100 — each part rendered in David's mimic of the TimeBack player: one column of cards, revealed one at a time by Continue. Every page's blue bar has Previous / Next, so you can walk the whole topic.

A lesson page: the video (or, until it exists, what it will say) → its one question → the whole article, one card per subtitle, figures where they belong → the quiz.

What the mimic cannot show. On the real platform the video is a separate activity before the lesson; here it sits in the first card. Typed-word answers and put-in-order tasks, which the player has but the mimic does not, appear as "Practice" cards with the answer printed. The intro poll is a pick where every reply is right. Two-option questions show as two-option MCQs (on the real platform they become a two-word pick). The PP100 is a note; its bank is on the reviewer page.

Tip: add #auto=end to a page's address to see it fully revealed and answered; #auto=wrong shows the red retry state.