:root {
    --bg: #ebf4f8;
    --surface: #ffffff;
    --border: #cbd5e1;
    --text: #334155;
    --text-muted: #64748b;
    --text-heading: #0f172a;
    --primary: #0284c7;
    --primary-light: #e0f2fe;
    --danger: #ef4444;
    --danger-light: #fee2e2;
    --success: #10b981;
    --shadow-sm: 0 4px 6px -1px rgba(2, 132, 199, 0.05);
    --shadow-md: 0 12px 30px -5px rgba(2, 132, 199, 0.1);
}

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

body {
    font-family: 'Inter', sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    line-height: 1.6;
    overflow-x: hidden;
}

/* 🌊 CANVAS NỀN: Sóng biển đa tầng chạy ngầm ngắt quãng */
#waveCanvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
    opacity: 0.85;
}

.main-wrap {
    position: relative;
    z-index: 2;
}

/* 🌊 HEADER: Hiệu ứng sóng cuộn chân Header ngăn cách bãi cát */
.header {
    background: linear-gradient(180deg, #ffffff 0%, #f0f9ff 100%);
    position: relative;
    padding: 2rem 0 4.5rem 0;
    box-shadow: var(--shadow-sm);
}

.header-container {
    max-width: 1340px;
    margin: 0 auto;
    padding: 0 1.5rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
    gap: 0.5rem;
    position: relative;
    z-index: 5;
}

@media (min-width: 992px) {
    .header-container {
        flex-direction: row;
        justify-content: space-between;
        text-align: left;
    }
}

/* Hệ thống sóng SVG lệch pha */
.ocean-waves {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 40px;
    overflow: hidden;
}

.ocean-waves svg {
    position: absolute;
    bottom: 0;
    width: 200%;
    height: 100%;
    transform: translate3d(0, 0, 0);
}

.wave-layer-1 {
    fill: rgba(2, 132, 199, 0.12);
    animation: waveMove 12s linear infinite;
    z-index: 3;
}

.wave-layer-2 {
    fill: rgba(14, 165, 233, 0.08);
    animation: waveMoveReverse 9s linear infinite;
    z-index: 2;
    bottom: 2px !important;
}

.wave-layer-3 {
    fill: var(--bg);
    animation: waveMove 18s linear infinite;
    z-index: 4;
    bottom: -1px !important;
}

@keyframes waveMove {
    0% {
        transform: translateX(0);
    }

    100% {
        transform: translateX(-50%);
    }
}

@keyframes waveMoveReverse {
    0% {
        transform: translateX(-50%);
    }

    100% {
        transform: translateX(0);
    }
}

.header-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    background: var(--danger-light);
    color: var(--danger);
    border: 1px solid rgba(239, 68, 68, 0.2);
    padding: 6px 16px;
    border-radius: 30px;
    font-size: 0.75rem;
    font-weight: 600;
    letter-spacing: 1px;
    text-transform: uppercase;
}

.header-badge .dot {
    width: 8px;
    height: 8px;
    background: var(--danger);
    border-radius: 50%;
    animation: blink 1.2s infinite;
}

@keyframes blink {
    0% {
        transform: scale(0.95);
        box-shadow: 0 0 0 0 rgba(239, 68, 68, 0.5);
    }

    70% {
        transform: scale(1);
        box-shadow: 0 0 0 8px rgba(239, 68, 68, 0);
    }

    100% {
        transform: scale(0.95);
        box-shadow: 0 0 0 0 rgba(239, 68, 68, 0);
    }
}

.header h1 {
    font-size: 1.85rem;
    font-weight: 700;
    color: var(--text-heading);
    margin-bottom: 0.1rem;
    letter-spacing: -0.5px;
}

.header .subtitle {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--primary);
    letter-spacing: 1px;
    text-transform: uppercase;
    margin-bottom: 0;
}

/* Layout chính */
.container-main {
    max-width: 1340px;
    margin: 0 auto;
    padding: 2rem 1.5rem;
}

/* 🌊 CARD: Hiệu ứng luồng sóng phát sáng quét nhẹ mặt Card khi hover */
.card {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(8px);
    border: 1px solid var(--border);
    border-radius: 14px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-sm);
    position: relative;
    overflow: hidden;
    transition: transform 0.3s cubic-bezier(0.16, 1, 0.3, 1), box-shadow 0.3s ease;
}

.card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
    border-color: #93c5fd;
}

.card::after {
    content: '';
    position: absolute;
    top: 0;
    left: -150%;
    width: 50%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(14, 165, 233, 0.06), transparent);
    transform: skewX(-25deg);
    pointer-events: none;
}

.card:hover::after {
    left: 200%;
    transition: left 1.2s cubic-bezier(0.16, 1, 0.3, 1);
}

.card-label {
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text-heading);
    margin-bottom: 1.2rem;
    display: flex;
    align-items: center;
    gap: 8px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.card-label i {
    color: var(--primary);
}

/* Khu vực Drop-zone tải tệp */
.drop-zone {
    background: #f8fafc;
    border: 2px dashed var(--border);
    border-radius: 10px;
    padding: 1.2rem;
    height: 100%;
    transition: all 0.25s ease;
}

.drop-zone:hover {
    border-color: var(--primary);
    background: var(--primary-light);
}

.drop-zone label {
    font-weight: 600;
    font-size: 0.85rem;
    color: var(--text-heading);
    margin-bottom: 0.8rem;
    display: flex;
    align-items: center;
    gap: 6px;
}

.drop-zone input[type="file"] {
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text);
    font-size: 0.8rem;
    border-radius: 6px;
    width: 100%;
    padding: 6px;
}

.drop-zone input[type="file"]::file-selector-button {
    background: var(--primary-light);
    border: 1px solid rgba(2, 132, 199, 0.15);
    color: var(--primary);
    padding: 4px 12px;
    border-radius: 4px;
    cursor: pointer;
    font-family: 'Inter', sans-serif;
    font-size: 0.75rem;
    font-weight: 600;
}

/* Nút bấm tinh chỉnh tương thích hệ thống */
.btn {
    font-family: 'Inter', sans-serif;
    font-weight: 600;
    padding: 0.6rem 1.4rem;
    border-radius: 8px;
    border: 1px solid transparent;
    font-size: 0.8rem;
    letter-spacing: 0.3px;
    text-transform: uppercase;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-primary {
    background: var(--primary);
    color: white;
}

.btn-primary:hover {
    background: #0369a1;
    box-shadow: 0 4px 12px rgba(2, 132, 199, 0.25);
}

.btn-outline {
    border-color: var(--border);
    color: var(--text);
    background: var(--surface);
}

.btn-outline:hover {
    background: var(--primary-light);
    border-color: var(--primary);
    color: var(--primary);
}

.btn-danger {
    background: var(--danger);
    color: white;
}

.btn-danger:hover {
    background: #b91c1c;
    box-shadow: 0 4px 12px rgba(239, 68, 68, 0.25);
}

/* 🌊 SƠ ĐỒ CƠ CHẾ VẬT LÝ CHUẨN HOÁ THỦY LỰC */
.rip-diagram {
    position: relative;
    width: 100%;
    aspect-ratio: 16/10;
    background: linear-gradient(180deg, #0284c7 0%, #0ea5e9 40%, #bae6fd 75%, #fef08a 100%);
    border: 1px solid var(--border);
    border-radius: 12px;
    overflow: hidden;
    margin-bottom: 1.2rem;
}

.zone-tag {
    position: absolute;
    font-size: 0.6rem;
    font-weight: 700;
    background: rgba(15, 23, 42, 0.6);
    color: #fff;
    padding: 2px 6px;
    border-radius: 3px;
    z-index: 5;
}

.zone-tag.critical {
    background: var(--danger);
}

/* Phân vùng Đường bờ cát */
.shoreline {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    height: 18%;
    background: linear-gradient(180deg, #fef08a 0%, #fcd34d 100%);
    border-top: 2px dashed #eab308;
    z-index: 4;
}

.shore-text {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 1px;
    color: #92400e;
    white-space: nowrap;
}

/* Phân vùng Cổ dòng xiết (Rãnh hút thu hẹp) */
.rip-neck {
    position: absolute;
    bottom: 18%;
    left: 42%;
    width: 16%;
    top: 35%;
    background: rgba(239, 68, 68, 0.08);
    border-left: 1px dashed rgba(239, 68, 68, 0.3);
    border-right: 1px dashed rgba(239, 68, 68, 0.3);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.rip-neck .zone-tag {
    top: 5px;
    white-space: nowrap;
}

/* Chuỗi mũi tên đẩy thẳng ra biển */
.rip-arrow {
    color: var(--danger);
    font-size: 1.4rem;
    position: absolute;
    bottom: 0;
    animation: pushToSea 2s linear infinite;
    opacity: 0;
}

.rip-arrow.delay-1 {
    animation-delay: 0.6s;
}

.rip-arrow.delay-2 {
    animation-delay: 1.2s;
}

@keyframes pushToSea {
    0% {
        opacity: 0;
        transform: translateY(20px) scale(0.8);
    }

    30% {
        opacity: 1;
    }

    100% {
        opacity: 0;
        transform: translateY(-80px) scale(1);
    }
}

/* Phân vùng Dòng trung chuyển dọc bờ (Feeder) */
.feeder-channels {
    position: absolute;
    bottom: 18%;
    left: 0;
    right: 0;
    height: 12%;
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0 10px;
    pointer-events: none;
}

.feeder {
    font-size: 0.6rem;
    font-weight: 800;
    color: #0369a1;
    opacity: 0.75;
}

/* Phân vùng Đầu dòng loang rộng ra khơi (Head) */
.rip-head {
    position: absolute;
    top: 0;
    left: 25%;
    width: 50%;
    height: 35%;
    background: rgba(2, 132, 199, 0.15);
    border-radius: 0 0 50% 50%;
}

.rip-head .zone-tag {
    bottom: 8px;
    left: 50%;
    transform: translateX(-50%);
}

.disperse-arrow {
    position: absolute;
    top: 40%;
    color: #0284c7;
    font-size: 1.1rem;
    animation: fanOut 2s ease-in-out infinite;
}

.disperse-arrow.left {
    left: 15%;
}

.disperse-arrow.right {
    right: 15%;
}

@keyframes fanOut {
    0% {
        transform: scale(0.8);
        opacity: 0.5;
    }

    50% {
        opacity: 1;
    }

    100% {
        transform: scale(1.2) translateX(var(--tx, 0));
        opacity: 0;
    }
}

.disperse-arrow.left {
    --tx: -15px;
}

.disperse-arrow.right {
    --tx: 15px;
}

/* Chỉ hướng Luồng bơi thoát hiểm song song */
.escape-route {
    position: absolute;
    top: 50%;
    background: var(--success);
    color: white;
    font-size: 0.58rem;
    font-weight: 700;
    padding: 4px 8px;
    border-radius: 4px;
    box-shadow: 0 2px 6px rgba(16, 185, 129, 0.3);
}

.escape-route.left {
    left: 5%;
}

.escape-route.right {
    right: 5%;
}

/* Box ảnh chỉ dẫn */
.instruct-box {
    border: 1px solid var(--border);
    border-radius: 10px;
    overflow: hidden;
    transition: all 0.3s ease;
    background: #fff;
}

.instruct-box:hover {
    border-color: var(--primary);
}

.instruct-img-wrap {
    width: 100%;
    aspect-ratio: 4/3;
    overflow: hidden;
    background: #f8fafc;
    position: relative;
}

.instruct-img-wrap img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    transition: transform 0.5s ease;
}

.instruct-box:hover img {
    transform: scale(1.04);
}

.instruct-desc {
    padding: 0.6rem 0.8rem;
    font-size: 0.78rem;
    font-weight: 600;
    text-align: center;
    color: var(--text-heading);
    background: #f8fafc;
    border-top: 1px solid var(--border);
}

/* Khối cấu trúc các bước kỹ năng */
.step {
    display: flex;
    gap: 12px;
    align-items: flex-start;
    padding: 0.6rem;
    border-radius: 8px;
    margin-bottom: 0.4rem;
}

.step-num {
    width: 26px;
    height: 26px;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--danger-light);
    border: 1px solid rgba(239, 68, 68, 0.15);
    color: var(--danger);
    font-weight: 700;
    font-size: 0.75rem;
    border-radius: 6px;
}

.step-num.safe {
    background: #d1fae5;
    border-color: rgba(16, 185, 129, 0.15);
    color: var(--success);
}

.step-content {
    font-size: 0.82rem;
    color: var(--text);
}

/* Footer */
.footer {
    background: var(--surface);
    border-top: 1px solid var(--border);
    padding: 1.5rem 0;
    margin-top: 4rem;
    text-align: center;
    font-size: 0.8rem;
    color: var(--text-muted);
    position: relative;
    z-index: 2;
}

/* Pulse animation for danger warnings */
@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}
.animate-pulse {
    animation: pulse 1.5s infinite ease-in-out;
    display: inline-block;
}