owl/docs/playground/samples/window_manager/window_manager.css

body {
    margin: 0;
}

.app {
    width: 100%;
    height: 100%;
    display: grid;
    grid-template-rows: auto 50px;
}

.window-manager {
    position: relative;
    width: 100%;
    height: 100%;
    background-color: #eeeeee;
    overflow: hidden;
}

.menubar {
    background-color: #875a7b;
    color: white;
}

.menubar button {
    height: 40px;
    font-size: 18px;
    margin: 5px;
}

.window {
    display: grid;
    grid-template-rows: 30px auto;
    border: 1px solid gray;
    background-color: white;
    position: absolute;
    box-shadow: 1px 1px 2px 1px grey;
}

.window.dragging {
    opacity: 0.75;
}

.window .header {
    background-color: #875a7b;
    display: grid;
    grid-template-columns: auto 24px;
    color: white;
    line-height: 30px;
    padding-left: 5px;
    cursor: default;
    user-select: none;
}

.window .header .close {
    cursor: pointer;
    font-size: 22px;
    padding-left: 4px;
    padding-right: 4px;
    font-weight: bold;
}

.counter {
    font-size: 20px;
}
.counter button {
    width: 80px;
    height:40px;
    font-size: 20px;
}