Introducing line charts

First let's start with a single series line chart. We will use one of the many data provided by The World Bank organization at www.worldbank.org. The following is the code snippet to create a simple line chart which shows the percentage of population ages, 65 and above, in Japan for the past three decades:

        var chart = new Highcharts.Chart({
            chart: {
                renderTo: 'container'
            },
            title: {
                text: 'Population ages 65 and over (% of total)',
            },
            credits: { 
               position: {
                  align: 'left',
                  x: 20
               },
               text: 'Data from The World Bank'
            },
            yAxis: {
                title: {
                    text: 'Percentage %'
                }
            },
            xAxis: {
               categories: ['1980', '1981',
               '1982', ... ],
               labels: {
                   step...