simple line chart from dataset
A simple line chart displays monthly values from a small JSON dataset, plotting each data point as a grey circle. Hovering over a circle turns it red, enlarges it, reveals its numeric value above, and draws a dashed vertical line down to the x-axis. The visualization uses D3 v3 with SVG, employing an ordinal scale for x-positions, a linear scale for y-values, and mouseover/mouseout event handlers to animate the transitions.