class CircleTarget: RectBlock {
    hits: Object
    function hitTest(self: CircleTarget, mount: Mount, point: Point): Bool {
        return point.inCircle(40, 40, 40)
    }
    function paint(self: CircleTarget, mount: Mount, geometry: Bounds): DisplayList {
        drawing = RectBlock.paint(self, mount, geometry)
        drawing.commands.at(0).width = 80
        drawing.commands.at(0).radius = 40
        return drawing
    }
    function onEvent(self: CircleTarget, event: Event): Unit {
        self.hits.increment()
        event.stopPropagation()
    }
}
hits = ui.state(0)
background = ui.state(0)
circle = CircleTarget(160, 80, 0, "#237A45", hits)
root = Column(24, 16, circle, TextBlock("点击圆内计入圆；透明右半区域交给父容器"), TextBlock("圆内点击"), ui.textOf(hits, "value"), TextBlock("父容器点击"), ui.textOf(background, "value"))
connection = root.on("click", background.increment)
page = Page()
page.render(root)