Always under 30 FPS on BB10

import QtQuick 2.0

Rectangle {
    width: 450
    height: 800
    color: "gray"

    Rectangle {
        height: 600
        width: 600
        color: "lightblue"
        opacity: 0.5
        anchors.centerIn: parent
        RotationAnimation on rotation {
            id: anim
            from: 0
            to: 360
            duration: 5000
            loops: Animation.Infinite
        }
    }

    Text {
        text: "Click to accelerate"
        font.pixelSize: 40
        color: "black"
        anchors.centerIn: parent
    }

    MouseArea {
        anchors.fill: parent
        onClicked: {
            if (anim.duration > 500) {
                anim.duration -= anim.duration > 1000 ? 1000 : 500
                anim.restart()
            }
        }
    }
}