[data-ns="widgets/webcam"] {
    .widget-content {
        position: relative;

        .webcam-on-container {
            min-height: 240px;
            text-align: center;

            .webcam-viewport {
                max-width: 100%;
                height: auto;
            }
        }
        .webcam-off-container {
            padding: 10px;
            text-align: center;

            .icon-webcam {
                display: inline-block;
                height: 64px;
                width: 64px;
                background: url("images/64x64/webcam.png") no-repeat 0 0;
            }
        }
    }
}

[data-ns="widgets/webcam"] {
    .widget-content {
        position: relative;

        .webcam-on-container {
            min-height: 240px;
            text-align: center;

            .webcam-viewport {
                width: 100%;
                height: auto;
            }
        }
        .webcam-off-container {
            padding: 10px;
            text-align: center;

            .icon-webcam {
                display: inline-block;
                height: 64px;
                width: 64px;
                background: url("images/64x64/webcam.png") no-repeat 0 0;
            }
        }
    }
}

Set the webcam viewport width to 100%
Set the webcam viewport width to 100%
