@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
    .timeslot .task .arrow {
        background: url(../img/timeline-left-arrow@2x.png) no-repeat;
        background-size: 100%
    }

    .timeslot.alt .task .arrow {
        background: url(../img/timeline-right-arrow@2x.png) no-repeat;
        background-size: 100%
    }

    ul.chat li.left .message .arrow {
        background: url(../img/chat-left@2x.png) no-repeat 0 0;
        background-size: 100%
    }

    ul.chat li.right .message .arrow {
        background: url(../img/chat-right@2x.png) no-repeat 0 0;
        background-size: 100%
    }
}