Show HN: Tufte's discrete sparklines using D3.js

Curious what the advantage is (in general) of sparklines over, say, a line of circles with filled in = win and empty = loss? you could use a red fill color for streaks of 4 or more. It seems to me a solution like that would have less clutter and better communicate the data...

What does the partial horizontal line indicate in Tufte's example?

Would have been better had you used SVG.