body {
    margin: 0;
    min-height: 100vh;
    background: #1a472a;
    font-family: 'Arial', sans-serif;
    display: flex;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow-x: hidden;
}

.snow-container {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    pointer-events: none;
    z-index: 1;
}

.calendar-container {
    background: #c41e3a;
    padding: 2rem;
    border-radius: 15px;
    box-shadow: 0 0 20px rgba(0,0,0,0.3);
    z-index: 2;
    margin: 20px;
}

h1 {
    color: #fff;
    text-align: center;
    margin-bottom: 2rem;
    text-shadow: 2px 2px 4px rgba(0,0,0,0.3);
}

.calendar {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 15px;
    max-width: 800px;
}

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

.door-front, .door-back {
    position: absolute;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    backface-visibility: hidden;
    transition: transform 0.6s;
    border-radius: 10px;
}

.door-front {
    background: #2f5d4b;
    color: #fff;
    font-size: 1.5em;
    font-weight: bold;
    border: 2px solid #fff;
}

.door.locked {
    cursor: not-allowed;
    opacity: 0.7;
}

.door.opened .door-front {
    transform: rotateY(180deg);
}

.day-number {
    position: relative;
    z-index: 2;
}

.lock {
    position: absolute;
    top: 5px;
    right: 5px;
    font-size: 0.8em;
}

.modal {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.7);
    z-index: 100;
}

.modal-content {
    background: #fff;
    margin: 15% auto;
    padding: 20px;
    width: 70%;
    max-width: 500px;
    border-radius: 10px;
    position: relative;
    text-align: center;
}

.close {
    position: absolute;
    right: 10px;
    top: 5px;
    font-size: 24px;
    cursor: pointer;
}

button#revealAnswer {
    background: #c41e3a;
    color: white;
    border: none;
    padding: 10px 20px;
    border-radius: 5px;
    margin: 15px 0;
    cursor: pointer;
    font-size: 1.1em;
}

button#revealAnswer:hover {
    background: #a01830;
}

@media (max-width: 600px) {
    .calendar {
        grid-template-columns: repeat(3, 1fr);
    }
}

@media (max-width: 400px) {
    .calendar {
        grid-template-columns: repeat(2, 1fr);
    }
}