.advent-calendar {
	width: 100%;
	background: #00520c;
	padding: 20px;
	border-radius: 10px;
	box-shadow: 0 0 20px rgba(0, 0, 0, 0.3);
}

.calendar-grid {
	display: grid;
	grid-template-columns: repeat(6, 1fr);
	gap: 10px;
}

.door {
	position: relative;
	perspective: 1000px;
	aspect-ratio: 1;
}

.door-front,
.door-back {
	position: absolute;
	width: 100%;
	height: 100%;
	display: flex;
	justify-content: center;
	align-items: center;
	font-size: 1.5em;
	border-radius: 5px;
	transition: transform 0.6s;
	backface-visibility: hidden;
	cursor: pointer;
}

.door-front {
	background: #e74c3c;
	transform: rotateY(0deg);
	color: white;
	font-weight: bold;
	box-shadow: 2px 2px 5px rgba(0, 0, 0, 0.2);
}

.door-back {
	background: #f7f703;
	transform: rotateY(180deg);
	font-size: 1em;
}

.door-back#door-link {
	font-size: 0.8rem;
}

.door-checkbox {
	display: none;
}

.day>input:checked+.door>.door-front {
	transform: rotateY(180deg);
}

.day>input:checked+.door>.door-front+.door-back {
	transform: rotateY(360deg);
}

@media (max-width: 600px) {
	.calendar-grid {
		grid-template-columns: repeat(4, 1fr);
	}
}

@media (max-width: 400px) {
	.calendar-grid {
		grid-template-columns: repeat(3, 1fr);
	}
}