Tangram scene with multiple data sources

scene.yaml

scene:
    background:
        color: lightblue

sources:
    earth:
        type: TopoJSON
        url:  //vector.mapzen.com/osm/earth/{z}/{x}/{y}.topojson
        
    landuse:
        type: TopoJSON
        url:  //vector.mapzen.com/osm/landuse/{z}/{x}/{y}.topojson

    roads:
        type: TopoJSON
        url:  //vector.mapzen.com/osm/roads/{z}/{x}/{y}.topojson
        
layers:
    earth:
        data:
            source: earth
        draw:
            polygons:
                order: 0
                color: darkgrey

    landuse:
        data:
            source: landuse
        draw:
            polygons:
                order: 1
                color: palegreen

    roads:
        data:
            source: roads
        draw:
            lines:
                order: 2
                color: white
                width: 2px