html{
	font-size: 20px;
}      

	  .rect-container {
            width: 500px;
            height: 300px;
            margin: 20px auto;
            border: none;
            overflow: hidden;
            position: relative;
        }
        .rect-grid {
            width: 80%;
            height: 80%;
            position: absolute;
            left: 10%;
            top: 10%;
            background-color: #f0f0f0;
            transition: all 1s ease;
        }
        .grid-line {
            position: absolute;
            background-color: #333;
        }
        .grid-line.vertical {
            width: 1px;
            height: 100%;
        }
        .grid-line.horizontal {
            width: 100%;
            height: 1px;
        }
        .grid-cell {
            position: absolute;
            width: 20%;
            height: 20%;
            display: flex;
            justify-content: center;
            align-items: center;
            box-sizing: border-box;
            border: 1px solid rgba(0, 0, 0, 0.1);
            background-color: rgba(255, 255, 255, 0.3);
        }
        #expand-rect-button {
            display: block;
            margin: 10px auto;
            padding: 8px 16px;
            cursor: pointer;
        }