body { font-family: sans-serif; padding: 20px; }
h3 { margin-top: 0; }

.container { 
    border: 2px dashed #ccc; 
    margin-bottom: 20px; 
    padding: 10px; 
}
.item { 
    background-color: #e0f7fa; 
    border: 1px solid #00796b; 
    padding: 10px; 
    width: 150px;
}

.display-block { display: block; margin-bottom: 5px; }
.display-inline { display: inline; width: auto; }
.display-flex { display: flex; }

.box {
    width: 200px;
    height: 100px;
    padding: 20px; 
    border: 5px solid #c2185b;
    margin: 15px;
    background-color: #fce4ec;
}

.content-box {
    box-sizing: content-box; 
}

.border-box {
    box-sizing: border-box; 
}