* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Arial', 'ヒラギノ丸ゴ Pro', 'Hiragino Maru Gothic Pro', sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    position: relative;
    overflow-x: hidden;
}

/* 星のアニメーション背景 */
.stars {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
}

.stars::before,
.stars::after {
    content: '⭐';
    position: absolute;
    font-size: 20px;
    animation: twinkle 3s infinite;
}

@keyframes twinkle {
    0%, 100% { opacity: 0.3; }
    50% { opacity: 1; }
}

.stars::before {
    top: 10%;
    left: 10%;
    animation-delay: 0s;
}

.stars::after {
    top: 20%;
    right: 15%;
    animation-delay: 1.5s;
}

/* コンテナ */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 40px 20px;
    position: relative;
    z-index: 1;
}

/* ヘッダー */
header {
    text-align: center;
    color: white;
    margin-bottom: 50px;
    animation: slideDown 0.8s ease-out;
}

@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.title {
    font-size: 3em;
    font-weight: bold;
    margin-bottom: 10px;
    text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.3);
}

.subtitle {
    font-size: 1.2em;
    opacity: 0.95;
}

/* カウントダウンセクション */
.countdown-section {
    margin-bottom: 60px;
    animation: scaleIn 0.8s ease-out 0.2s both;
}

@keyframes scaleIn {
    from {
        opacity: 0;
        transform: scale(0.9);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

.countdown-display {
    display: flex;
    justify-content: center;
    gap: 20px;
    flex-wrap: wrap;
}

.countdown-box {
    background: white;
    border-radius: 20px;
    padding: 30px 25px;
    min-width: 100px;
    text-align: center;
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.countdown-box:hover {
    transform: translateY(-10px);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.3);
}

.countdown-number {
    font-size: 3.5em;
    font-weight: bold;
    color: #667eea;
    line-height: 1;
    margin-bottom: 10px;
}

.countdown-label {
    font-size: 1.1em;
    color: #764ba2;
    font-weight: bold;
}

/* 夏休みの活動セクション */
.summer-activities {
    background: white;
    border-radius: 20px;
    padding: 40px;
    margin-bottom: 40px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.15);
}

.summer-activities h2 {
    text-align: center;
    font-size: 2.2em;
    color: #667eea;
    margin-bottom: 30px;
}

.activity-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
    gap: 20px;
}

.card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    border-radius: 15px;
    padding: 25px 20px;
    text-align: center;
    color: white;
    cursor: pointer;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    box-shadow: 0 5px 15px rgba(102, 126, 234, 0.3);
}

.card:hover {
    transform: translateY(-8px) scale(1.05);
    box-shadow: 0 15px 30px rgba(102, 126, 234, 0.5);
}

.card .emoji {
    display: block;
    font-size: 3em;
    margin-bottom: 10px;
}

.card p {
    font-size: 1em;
    font-weight: bold;
    line-height: 1.4;
}

/* 新学期準備セクション */
.preparation {
    background: white;
    border-radius: 20px;
    padding: 40px;
    margin-bottom: 40px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.15);
}

.preparation h2 {
    text-align: center;
    font-size: 2.2em;
    color: #667eea;
    margin-bottom: 30px;
}

.checklist {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.check-item {
    display: flex;
    align-items: center;
    padding: 15px 20px;
    background: #f0f0f0;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    font-size: 1.1em;
    font-weight: 500;
    color: #333;
}

.check-item:hover {
    background: #e0e0ff;
    transform: translateX(5px);
}

.check-item input[type="checkbox"] {
    width: 24px;
    height: 24px;
    margin-right: 15px;
    cursor: pointer;
    accent-color: #667eea;
}

.check-item input[type="checkbox"]:checked + span {
    text-decoration: line-through;
    color: #999;
}

/* メッセージセクション */
.message {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    text-align: center;
    border-radius: 20px;
    padding: 40px 30px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.2);
    animation: slideUp 0.8s ease-out 0.4s both;
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.message p {
    font-size: 1.5em;
    font-weight: bold;
    margin-bottom: 10px;
    text-shadow: 1px 1px 2px rgba(0, 0, 0, 0.2);
}

.message-sub {
    font-size: 1.2em;
    opacity: 0.95;
    margin: 0;
}

/* レスポンシブデザイン */
@media (max-width: 768px) {
    .title {
        font-size: 2em;
    }

    .subtitle {
        font-size: 1em;
    }

    .countdown-display {
        gap: 10px;
    }

    .countdown-box {
        padding: 20px 15px;
        min-width: 80px;
    }

    .countdown-number {
        font-size: 2.5em;
    }

    .countdown-label {
        font-size: 0.9em;
    }

    .summer-activities,
    .preparation,
    .message {
        padding: 30px 20px;
    }

    .summer-activities h2,
    .preparation h2 {
        font-size: 1.8em;
    }

    .activity-cards {
        grid-template-columns: repeat(auto-fit, minmax(110px, 1fr));
        gap: 15px;
    }

    .card .emoji {
        font-size: 2.5em;
    }

    .message p {
        font-size: 1.2em;
    }

    .message-sub {
        font-size: 1em;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 20px 15px;
    }

    .title {
        font-size: 1.5em;
    }

    .countdown-display {
        gap: 8px;
    }

    .countdown-box {
        padding: 15px 10px;
        min-width: 70px;
    }

    .countdown-number {
        font-size: 2em;
    }

    .countdown-label {
        font-size: 0.8em;
    }

    .activity-cards {
        grid-template-columns: repeat(2, 1fr);
    }

    .card {
        padding: 20px 15px;
    }

    .card .emoji {
        font-size: 2em;
    }
}