I find I have to think about them too long, and I think the rendering details contribute to that. There is nothing wrong with double y-axis graphs if you don't

I find I have to think about them too long, and I think the rendering details contribute to that. There is nothing wrong with double y-axis graphs if you don't just slap them together because the x-axis has the same range. I think the lack of concern for the rendering details make these harder to immediately read than they should be. Why are the axis labels not colored the same way the lines are, or the entries in the key not positionally associated with their axis (rather than being in the center). The triangles and circles on the lines on "Steam Sales" offer no utility (except, perhaps, for color-blindness or if it was printed in black-and-white, but then dotted-vs-solid would be a better choice). There are horizontal tic marks, but they are separating the dates, not centered on the datapoint, meaning the data is being presented as a column, which a line graph is not best for (that is, the choice of graph given this data may not be the best one). And that's just the problem with one graph. There are two graphs on this page, and both have different rendering details. Consistency is important because it means understanding the rendering of one graph translates to the understanding of the other. Why doesn't the second graph have shapes over the data points? Why doesn't the second graph have tic marks along the x-axis? Color is used inconsistently: the unit for the blue line is units sold in the first one and dollars in the second one, and the side the graph the blue line is associated with switches. Despite that the axes that are denominated in dollars are showing different things (totals vs discrete values), there is value in having them both on the same side of the graph (and in the same color)—that the blue one switches sides means the viewer needs to concentrate harder on the key and layout leaving less time for interpreting the data. It would actually be better if four colors between the two graphs were used since there are four different domains of data being shown. They both show the same time range, but the dates are not formatted similarly along the x-axis. In both cases, the units on the labels are too exact. "60.00%": why is this 4 significant digits, a whole number percentage would do. At this size, the decimal point and percent sign almost get lost with the unneeded zeros. "Steam Sales" has units that are so big with so many zeros you have to think about the order of magnitude; these should be truncated to "$300M" and "65M".