:root {
    /* Primary Colors */
    --primary-dark: #031448;
    --background-light: rgba(237, 246, 255, 1);
    --alice-blue: aliceblue;

    /* Driftwood Color Palette */
    --color-Driftwood-50: #f8f6ee;
    --color-Driftwood-100: #eee8d3;
    --color-Driftwood-200: #dfd1a9;
    --color-Driftwood-300: #cdb277;
    --color-Driftwood-400: #bd9852;
    --color-Driftwood-500: #a47d40;
    --color-Driftwood-600: #956a39;
    --color-Driftwood-700: #785030;
    --color-Driftwood-800: #65432e;
    --color-Driftwood-900: #58392b;
    --color-Driftwood-950: #321e16;

    /* Bunting Color Palette */
    --color-Bunting-50: #edf6ff;
    --color-Bunting-100: #d7e9ff;
    --color-Bunting-200: #b7d9ff;
    --color-Bunting-300: #86c3ff;
    --color-Bunting-400: #4da2ff;
    --color-Bunting-500: #247bff;
    --color-Bunting-600: #0d58ff;
    --color-Bunting-700: #0641ef;
    --color-Bunting-800: #0c36c1;
    --color-Bunting-900: #113397;
    --color-Bunting-950: #0d1b4c;

    /* Accent Colors */
    --accent-color: #a5803f;
    --accent-hover: #8b6b33;

    /* Text Colors */
    --text-light: white;
    --text-dark: rgba(33, 37, 41, 1);

    /* Border & Separator Colors */
    --border-accent: #a5803f;
    --border-highlight: #0d6efd;

    /* Bootstrap-like Colors (if applicable) */
    --blue-bootstrap: #0d6efd;

    /* Font Families */
    --font-family-inter: "Inter", sans-serif;

    /* Spacing & Sizing (Optional, but good practice) */
    --font-sm: 0.875rem;
    --font-general: 1rem;
    --font-xl: 1.25rem;

    --h1-min-font: 1.75rem;
    --h1-preferred-font: 2vw + 0.75rem;
    --h1-max-font: 2.5rem;

    --h2-min-font: 1.25rem;
    --h2-preferred-font: 1.25vw + 0.5rem;
    --h2-max-font: 1.5rem;

    --h3-min-font: 1.125rem;
    --h3-preferred-font: 1vw + 0.5rem;
    --h3-max-font: 1.25rem;

    --h4-min-font: 1rem;
    --h4-preferred-font: 0.9vw + 0.4rem;
    --h4-max-font: 1.125rem;

    --h5-min-font: 0.875rem;
    --h5-preferred-font: 0.8vw + 0.4rem;
    --h5-max-font: 1rem;
    /* Responsive Font Sizing Variables */
    --register-number-min-font: 4.5rem;
    --register-number-preferred-font: 4vw + 1rem;
    --register-number-max-font: 6.25rem;

    --text-step-register-min-font: 1.5rem;
    --text-step-register-preferred-font: 1.5vw + 0.75rem;
    --text-step-register-max-font: 2rem;

    --section-title-h2-min-font: 1.25rem;
    --section-title-h2-preferred-font: 1.25vw + 0.5rem;
    --section-title-h2-max-font: 1.5rem;

    --text-section-register-min-font: 1.125rem;
    --text-section-register-preferred-font: 1vw + 0.75rem;
    --text-section-register-max-font: 1.75rem;

    --highlight-callout-min-font: 1.125rem;
    --highlight-callout-preferred-font: 1.2vw + 0.5rem;
    --highlight-callout-max-font: 1.5rem;

    --cert-title-min-font: 1rem;
    --cert-title-preferred-font: 2vw + 0.5rem;
    --cert-title-max-font: 1.75rem;

    --price-font-min: 1.125rem;
    --price-font-preferred: 2vw + 0.5rem;
    --price-font-max: 1.5rem;

    --tesol-ribbon-min-font: 1.5rem;
    --tesol-ribbon-preferred-font: 3vw + 0.5rem;
    --tesol-ribbon-max-font: 2.5rem;

    --detail-list-min-font: 0.9rem;
    --detail-list-preferred-font: 1.5vw + 0.3rem;
    --detail-list-max-font: 1.25rem;

    /* New Responsive Font Sizing Variables for Course Cards */
    --card-title-min-font: 1.125rem; /* 18px */
    --card-title-preferred-font: 2vw + 0.5rem;
    --card-title-max-font: 1.5rem; /* 24px */

    --card-list-min-font: 0.8rem; /* 12.8px (slightly smaller than small) */
    --card-list-preferred-font: 1.2vw + 0.2rem;
    --card-list-max-font: 0.9rem; /* 14.4px (original small is 0.875rem ~ 14px) */

    --card-price-old-min-font: 0.8rem;
    --card-price-old-preferred-font: 1.5vw + 0.3rem;
    --card-price-old-max-font: 1rem; /* Original 1rem */

    --card-price-new-min-font: 1rem;
    --card-price-new-preferred-font: 2.2vw + 0.5rem;
    --card-price-new-max-font: 1.3rem; /* Slightly larger than 1.25rem (fs-5) */

    --line-height-general: 24px;
    --line-height-xl: 30px;
    --bg-gradient: linear-gradient(to right, #ffffff 32.72%, #d7e9ff 79.43%);

    --font-weight-general: 400;
    --font-weight-sm: 300;
    --font-weight-step-register: 700;

    --padding-section: 60px 0;
    --border-radius-sm: 5px;
    --border-radius-md: 0.5rem;
    --gap-md: 1rem;
    --margin-bottom-lg: 2rem;
    --height-line: 2px;
    --max-width-line: 100px;
}

html {
    scroll-behavior: smooth;
}
body {
    font-family: var(--font-family-inter);
    font-size: 16px;
    background-color: #f8f9fa;
    color: var(--text-dark);
}
h1,
h2,
h3,
h4,
h5 {
    font-family: var(--font-family-inter);
    color: var(--text-dark);
    line-height: 1.2;
    margin-bottom: 0.5rem;
}

h1 {
    font-size: clamp(var(--h1-min-font), var(--h1-preferred-font), var(--h1-max-font));
    font-weight: 700;
}

h2 {
    font-size: clamp(var(--h2-min-font), var(--h2-preferred-font), var(--h2-max-font));
    font-weight: 600;
}

h3 {
    font-size: clamp(var(--h3-min-font), var(--h3-preferred-font), var(--h3-max-font));
    font-weight: 600;
}

h4 {
    font-size: clamp(var(--h4-min-font), var(--h4-preferred-font), var(--h4-max-font));
    font-weight: 500;
}

h5 {
    font-size: clamp(var(--h5-min-font), var(--h5-preferred-font), var(--h5-max-font));
    font-weight: 500;
}
.btn-authen {
    font-size: var(--font-sm);
    font-weight: 500;
    padding: 0.5rem 1.2rem;
    border-radius: var(--border-radius-md);
    background-color: var(--color-Bunting-700);
    color: var(--text-light);
    border: 1px solid var(--color-Bunting-700);
    transition: background-color 0.3s ease, transform 0.2s ease;
}
.dropdown-toggle:after {
    vertical-align: 0px !important;
    margin-left: 0px;
}
.btn-authen:hover {
    background-color: var(--color-Bunting-900);
    transform: translateY(-2px);
}

.btn-out-line-authen {
    font-size: var(--font-sm);
    font-weight: 500;
    padding: 0.5rem 1.2rem;
    border-radius: var(--border-radius-md);
    background-color: transparent;
    border: 1px solid var(--color-Bunting-700);
    color: var(--color-Bunting-700);
    transition: background-color 0.3s ease, color 0.3s ease, transform 0.2s ease;
}

.btn-out-line-authen:hover {
    background-color: var(--color-Bunting-700);
    color: var(--text-light);
    transform: translateY(-2px);
}

#home {
    padding-top: 120px; /* Thay thế 120px bằng chiều cao thực tế của header fixed-top của bạn */
}

#home .video-container {
    /* Giả sử bạn thêm div này */
    padding-top: 120px; /* Áp dụng cho div container nếu #home có các thuộc tính khác ảnh hưởng */
}
strong {
    color: var(--text-dark);
}

.section {
    padding: 60px 0;
}

.bg-gradient-web {
    background-image: var(--bg-gradient);
}

.bg-primary-dark {
    background-color: #031448;
}

.bg-primary {
    background-color: var(--color-Bunting-50) !important;
}

.text-accent {
    color: #a5803f;
}

.btn-accent {
    background-color: #a5803f;
    color: white;
}

.btn-accent:hover {
    background-color: #8b6b33;
}

.text-about-us {
    font-size: var(--font-xl);
    font-weight: var(--font-weight-sm);
    line-height: var(--line-height-xl);
    color: var(--text-dark);
    text-align: center;
}

.card:hover {
    transform: scale(1.02);
    transition: 0.3s ease-in-out;
}

.tooltip-inner {
    max-width: 200px;
}

.icon-tooltip {
    cursor: pointer;
}

.section-title {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 2rem;
}

.section-title::before,
.section-title::after {
    content: "";
    flex: 1;
    height: 1px;
    background-color: var(--color-Bunting-800);
    max-width: 500px;
}

.section-title h2 {
    margin: 0;
    padding: 0.25rem 1rem;
    border: 2px solid var(--color-Bunting-900);
    border-radius: 30px;
    font-weight: 500;
    font-size: clamp(
        var(--section-title-h2-min-font),
        var(--section-title-h2-preferred-font),
        var(--section-title-h2-max-font)
    );
    color: var(--text-light);
    background-color: var(--color-Bunting-800);
}

.hover-scale {
    transition: transform 0.3s ease;
}
.hover-scale-border {
    transition: transform 0.3s ease;
    border-left: 5px solid var(--color-Bunting-800);
}
.hover-scale:hover {
    transform: scale(1.05);
}

.text-general {
    font-size: var(--font-general);
    font-weight: var(--font-weight-general);
    line-height: var(--line-height-general);
    color: var(--text-dark);
    text-align: start;
}

.text-section-register {
    font-size: clamp(
        var(--text-section-register-min-font),
        var(--text-section-register-preferred-font),
        var(--text-section-register-max-font)
    );
    font-weight: var(--font-weight-general);
    line-height: 2.25rem;
    padding-top: var(--font-xl);
    letter-spacing: 0;
    color: rgba(0, 0, 0, 0.5);
    text-align: start;
}

.counter {
    font-size: 2rem;
    font-weight: bold;
    color: var(--text-dark);
}

.highlight-callout {
    background-color: var(--color-Bunting-50);
    border-left: 5px solid var(--color-Bunting-800);
    padding: 1.5rem;
    font-size: clamp(
        var(--highlight-callout-min-font),
        var(--highlight-callout-preferred-font),
        var(--highlight-callout-max-font)
    );
    font-weight: 500;
    color: var(--color-Bunting-800);
    border-radius: 0.5rem;
}

.register-number {
    font-size: clamp(
        var(--register-number-min-font),
        var(--register-number-preferred-font),
        var(--register-number-max-font)
    );
    font-weight: bold;
    background: linear-gradient(to bottom, #74b9f9, #d7e9ff);

    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    color: transparent;

    display: inline-block;
    line-height: 1;
}

.text-step-register {
    font-size: clamp(
        var(--text-step-register-min-font),
        var(--text-step-register-preferred-font),
        var(--text-step-register-max-font)
    );
    font-weight: var(--font-weight-step-register);
}

.modal-header .modal-title {
    text-shadow: 0 1px 3px rgba(0, 0, 0, 0.5);
}
.bi-star-fill,
.bi-star {
    transition: transform 0.2s;
}
.bi-star-fill:hover,
.bi-star:hover {
    transform: scale(1.2);
}

/* New clamp classes for pricing/detail sections */
.clamp-cert-title {
    font-size: clamp(var(--cert-title-min-font), var(--cert-title-preferred-font), var(--cert-title-max-font));
}

.clamp-price-text {
    font-size: clamp(var(--price-font-min), var(--price-font-preferred), var(--price-font-max));
}

.clamp-tesol-ribbon {
    font-size: clamp(var(--tesol-ribbon-min-font), var(--tesol-ribbon-preferred-font), var(--tesol-ribbon-max-font));
}

.clamp-detail-list {
    font-size: clamp(var(--detail-list-min-font), var(--detail-list-preferred-font), var(--detail-list-max-font));
}

/* Responsive adjustment for 50% OFF sticker */
.tesol-sticker {
    width: 60px;
    height: auto;
}

@media (min-width: 768px) {
    .tesol-sticker {
        width: 90px;
    }
}

/* New clamp classes for Course Cards */
.clamp-card-title {
    font-size: clamp(var(--card-title-min-font), var(--card-title-preferred-font), var(--card-title-max-font));
}

.clamp-card-list {
    font-size: clamp(var(--card-list-min-font), var(--card-list-preferred-font), var(--card-list-max-font));
}

.clamp-card-price-old {
    font-size: clamp(
        var(--card-price-old-min-font),
        var(--card-price-old-preferred-font),
        var(--card-price-old-max-font)
    );
}

.clamp-card-price-new {
    font-size: clamp(
        var(--card-price-new-min-font),
        var(--card-price-new-preferred-font),
        var(--card-price-new-max-font)
    );
}
.custom-register-button {
    position: relative;
    overflow: hidden;
    transition: all 0.3s ease;
}

.custom-register-button.pulse {
    animation: pulse 1.5s infinite;
}

@keyframes pulse {
    0% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(0, 149, 255, 0.7);
    }
    70% {
        transform: scale(1.05);
        box-shadow: 0 0 0 20px rgba(255, 102, 0, 0);
    }
    100% {
        transform: scale(1);
        box-shadow: 0 0 0 0 rgba(255, 102, 0, 0);
    }
}
.responsive-iframe-wrapper {
    position: relative;
    width: 100%;
    padding-bottom: 56.25%; /* Tỷ lệ 16:9 */
    height: 0;
    overflow: hidden;
}

.responsive-iframe-wrapper iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: 0;
}