/* =====================================================
 * 📱 APP.CSS - CSS Chính (Mobile-First)
 * EngViet Learn - Webapp học tiếng Anh
 * Ưu tiên Flexbox & CSS Grid cho mọi kích cỡ màn hình
 * ===================================================== */

/* === 🔄 RESET & BASE === */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-primary);
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-normal);
    line-height: var(--line-height-normal);
    color: var(--text-primary);
    background-color: var(--bg-primary);
    min-height: 100vh;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    /* Padding cho bottom nav trên mobile */
    padding-bottom: calc(var(--bottom-nav-height) + var(--safe-area-bottom) + 16px);
}

/* Ẩn bottom padding khi ở trang auth */
body.auth-page {
    padding-bottom: 0;
}

a {
    color: var(--primary);
    text-decoration: none;
    transition: color var(--transition-fast);
}

a:hover {
    color: var(--primary-dark);
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

ul,
ol {
    list-style: none;
}

button,
input,
select,
textarea {
    font-family: inherit;
    font-size: inherit;
}

/* === 📱 CONTAINER (Mobile-first) === */
.container {
    width: 100%;
    max-width: var(--max-width-mobile);
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

@media (min-width: 481px) {
    .container {
        max-width: var(--max-width-tablet);
    }
}

/* === 🔝 HEADER (Mobile App Bar) === */
.app-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    height: var(--header-height);
    background: var(--bg-secondary);
    border-bottom: 1px solid var(--border-light);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--spacing-md);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    background: rgba(255, 255, 255, 0.95);
}

.app-header__logo {
    font-family: var(--font-display);
    font-size: var(--font-size-lg);
    font-weight: var(--font-weight-extrabold);
    background: var(--bg-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.app-header__actions {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
}

.app-header__icon-btn {
    width: 40px;
    height: 40px;
    border-radius: var(--border-radius-full);
    border: none;
    background: transparent;
    color: var(--text-secondary);
    font-size: var(--font-size-lg);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-fast);
    position: relative;
}

.app-header__icon-btn:hover {
    background: var(--primary-bg);
    color: var(--primary);
}

.app-header__badge {
    position: absolute;
    top: 4px;
    right: 4px;
    width: 18px;
    height: 18px;
    border-radius: var(--border-radius-full);
    background: var(--danger);
    color: white;
    font-size: 10px;
    font-weight: var(--font-weight-bold);
    display: flex;
    align-items: center;
    justify-content: center;
}

/* === 📄 MAIN CONTENT === */
.main-content {
    margin-top: calc(var(--header-height) + var(--spacing-md));
    min-height: calc(100vh - var(--header-height) - var(--bottom-nav-height));
}

/* === 🧭 BOTTOM NAVIGATION (Mobile) === */
.bottom-nav {
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    height: calc(var(--bottom-nav-height) + var(--safe-area-bottom));
    padding-bottom: var(--safe-area-bottom);
    background: var(--bg-secondary);
    border-top: 1px solid var(--border-light);
    display: flex;
    align-items: center;
    justify-content: space-around;
    box-shadow: 0 -4px 16px rgba(0, 0, 0, 0.05);
}

.bottom-nav__item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 2px;
    padding: var(--spacing-xs) var(--spacing-sm);
    color: var(--text-light);
    font-size: var(--font-size-xs);
    font-weight: var(--font-weight-medium);
    text-decoration: none;
    transition: all var(--transition-fast);
    position: relative;
    min-width: 56px;
}

.bottom-nav__item i {
    font-size: 22px;
    transition: all var(--transition-fast);
}

.bottom-nav__item.active,
.bottom-nav__item:hover {
    color: var(--primary);
}

.bottom-nav__item.active i {
    transform: scale(1.1);
}

.bottom-nav__item.active::before {
    content: '';
    position: absolute;
    top: -1px;
    left: 50%;
    transform: translateX(-50%);
    width: 32px;
    height: 3px;
    background: var(--primary);
    border-radius: 0 0 4px 4px;
}

/* === 📦 CARDS === */
.card {
    background: var(--bg-secondary);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    box-shadow: var(--shadow-sm);
    transition: all var(--transition);
}

.card:hover {
    box-shadow: var(--shadow);
}

.card--gradient {
    background: var(--bg-gradient);
    color: white;
}

.card--outlined {
    background: transparent;
    border: 2px solid var(--border-color);
    box-shadow: none;
}

/* === 📊 PROGRESS BAR === */
.progress-bar {
    width: 100%;
    height: 8px;
    background: var(--border-light);
    border-radius: 100px;
    overflow: hidden;
    position: relative;
}

.progress-bar__fill {
    height: 100%;
    border-radius: 100px;
    background: var(--bg-gradient);
    transition: width var(--transition-slow);
    position: relative;
}

.progress-bar__fill::after {
    content: '';
    position: absolute;
    right: 0;
    top: 0;
    width: 20px;
    height: 100%;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 100px;
}

.progress-bar--lg {
    height: 12px;
}

.progress-bar--sm {
    height: 4px;
}

/* === 🔘 BUTTONS === */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-sm);
    padding: 12px 24px;
    border-radius: var(--border-radius);
    border: none;
    font-size: var(--font-size-base);
    font-weight: var(--font-weight-semibold);
    cursor: pointer;
    transition: all var(--transition);
    text-decoration: none;
    line-height: 1;
    white-space: nowrap;
    user-select: none;
    -webkit-tap-highlight-color: transparent;
}

.btn:active {
    transform: scale(0.96);
}

.btn--primary {
    background: var(--bg-gradient);
    color: white;
    box-shadow: var(--shadow-primary);
}

.btn--primary:hover {
    box-shadow: 0 6px 24px rgba(108, 92, 231, 0.4);
    transform: translateY(-1px);
}

.btn--secondary {
    background: var(--secondary);
    color: white;
    box-shadow: var(--shadow-success);
}

.btn--outline {
    background: transparent;
    color: var(--primary);
    border: 2px solid var(--primary);
}

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

.btn--ghost {
    background: transparent;
    color: var(--text-secondary);
}

.btn--ghost:hover {
    background: var(--primary-bg);
    color: var(--primary);
}

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

.btn--lg {
    padding: 16px 32px;
    font-size: var(--font-size-md);
    border-radius: var(--border-radius-lg);
}

.btn--sm {
    padding: 8px 16px;
    font-size: var(--font-size-sm);
    border-radius: var(--border-radius-sm);
}

.btn--full {
    width: 100%;
}

.btn--round {
    border-radius: 100px;
}

/* Nút đáp án cho bài tập (to, dễ bấm trên mobile) */
.btn--answer {
    width: 100%;
    padding: 18px 20px;
    font-size: var(--font-size-md);
    border-radius: var(--border-radius-lg);
    background: var(--bg-secondary);
    color: var(--text-primary);
    border: 2px solid var(--border-color);
    text-align: left;
    min-height: 56px;
    transition: all var(--transition);
}

.btn--answer:hover {
    border-color: var(--primary);
    background: var(--primary-bg);
}

.btn--answer.selected {
    border-color: var(--primary);
    background: var(--primary-bg);
    color: var(--primary);
}

.btn--answer.correct {
    border-color: var(--success);
    background: var(--success-bg);
    color: var(--success);
}

.btn--answer.incorrect {
    border-color: var(--danger);
    background: var(--danger-bg);
    color: var(--danger);
}

/* === 📝 FORM INPUTS === */
.form-group {
    margin-bottom: var(--spacing-md);
}

.form-label {
    display: block;
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-semibold);
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.form-input {
    width: 100%;
    padding: 14px 16px;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: var(--font-size-base);
    color: var(--text-primary);
    background: var(--bg-secondary);
    transition: all var(--transition-fast);
    outline: none;
}

.form-input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(108, 92, 231, 0.1);
}

.form-input::placeholder {
    color: var(--text-light);
}

.form-input--error {
    border-color: var(--danger);
}

.form-error {
    font-size: var(--font-size-xs);
    color: var(--danger);
    margin-top: var(--spacing-xs);
}

/* === 🔔 ALERTS / FLASH MESSAGES === */
.alert {
    padding: var(--spacing-md);
    border-radius: var(--border-radius);
    font-size: var(--font-size-sm);
    font-weight: var(--font-weight-medium);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
    animation: slideDown 0.3s ease;
}

.alert--success {
    background: var(--success-bg);
    color: #00856A;
    border-left: 4px solid var(--success);
}

.alert--error {
    background: var(--danger-bg);
    color: #C0392B;
    border-left: 4px solid var(--danger);
}

.alert--warning {
    background: var(--warning-bg);
    color: #976A00;
    border-left: 4px solid var(--warning);
}

.alert--info {
    background: var(--info-bg);
    color: #0066CC;
    border-left: 4px solid var(--info);
}

/* === 🏷️ BADGES === */
.badge {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    padding: 4px 10px;
    border-radius: 100px;
    font-size: var(--font-size-xs);
    font-weight: var(--font-weight-semibold);
    white-space: nowrap;
}

.badge--primary {
    background: var(--primary-bg);
    color: var(--primary);
}

.badge--success {
    background: var(--success-bg);
    color: var(--success);
}

.badge--warning {
    background: var(--warning-bg);
    color: #976A00;
}

.badge--danger {
    background: var(--danger-bg);
    color: var(--danger);
}

.badge--xp {
    background: linear-gradient(135deg, #F9CA24 0%, #F0932B 100%);
    color: white;
    font-weight: var(--font-weight-bold);
}

/* === 🔥 STREAK BADGE === */
.streak-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 6px 14px;
    border-radius: 100px;
    background: linear-gradient(135deg, #F0932B 0%, #E17055 100%);
    color: white;
    font-weight: var(--font-weight-bold);
    font-size: var(--font-size-sm);
}

.streak-badge i {
    font-size: var(--font-size-md);
}

/* === 🃏 FLASHCARD === */
/* (Chi tiết trong flashcard.css) */

/* === 📱 RESPONSIVE UTILITIES === */
.text-center {
    text-align: center;
}

.text-left {
    text-align: left;
}

.text-right {
    text-align: right;
}

.flex {
    display: flex;
}

.flex-col {
    flex-direction: column;
}

.flex-center {
    align-items: center;
    justify-content: center;
}

.flex-between {
    justify-content: space-between;
}

.flex-wrap {
    flex-wrap: wrap;
}

.gap-xs {
    gap: var(--spacing-xs);
}

.gap-sm {
    gap: var(--spacing-sm);
}

.gap-md {
    gap: var(--spacing-md);
}

.gap-lg {
    gap: var(--spacing-lg);
}

.mt-sm {
    margin-top: var(--spacing-sm);
}

.mt-md {
    margin-top: var(--spacing-md);
}

.mt-lg {
    margin-top: var(--spacing-lg);
}

.mt-xl {
    margin-top: var(--spacing-xl);
}

.mb-sm {
    margin-bottom: var(--spacing-sm);
}

.mb-md {
    margin-bottom: var(--spacing-md);
}

.mb-lg {
    margin-bottom: var(--spacing-lg);
}

.w-full {
    width: 100%;
}

.hidden {
    display: none !important;
}

.truncate {
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

/* === ✨ ANIMATIONS === */
@keyframes slideDown {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(10px);
    }

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

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

    to {
        opacity: 1;
        transform: scale(1);
    }
}

@keyframes pulse {

    0%,
    100% {
        opacity: 1;
    }

    50% {
        opacity: 0.5;
    }
}

@keyframes bounce {

    0%,
    100% {
        transform: translateY(0);
    }

    50% {
        transform: translateY(-6px);
    }
}

@keyframes shake {

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

    10%,
    30%,
    50%,
    70%,
    90% {
        transform: translateX(-4px);
    }

    20%,
    40%,
    60%,
    80% {
        transform: translateX(4px);
    }
}

@keyframes confetti {
    0% {
        transform: translateY(0) rotate(0deg);
        opacity: 1;
    }

    100% {
        transform: translateY(-200px) rotate(720deg);
        opacity: 0;
    }
}

.animate-slide-down {
    animation: slideDown 0.3s ease;
}

.animate-slide-up {
    animation: slideUp 0.3s ease;
}

.animate-fade-in {
    animation: fadeIn 0.3s ease;
}

.animate-scale-in {
    animation: scaleIn 0.3s ease;
}

.animate-pulse {
    animation: pulse 2s infinite;
}

.animate-bounce {
    animation: bounce 1s infinite;
}

.animate-shake {
    animation: shake 0.5s ease;
}

/* === 🖼️ SKELETON LOADING === */
.skeleton {
    background: linear-gradient(90deg, var(--border-light) 25%, #F5F5F5 50%, var(--border-light) 75%);
    background-size: 200% 100%;
    animation: shimmer 1.5s infinite;
    border-radius: var(--border-radius-sm);
}

@keyframes shimmer {
    0% {
        background-position: -200% 0;
    }

    100% {
        background-position: 200% 0;
    }
}

.skeleton--text {
    height: 16px;
    width: 80%;
    margin-bottom: 8px;
}

.skeleton--circle {
    width: 48px;
    height: 48px;
    border-radius: var(--border-radius-full);
}

.skeleton--card {
    height: 120px;
    width: 100%;
}

/* === 📱 MEDIA QUERIES === */
@media (min-width: 481px) {

    /* Tablet adjustments */
    .main-content {
        padding: 0 var(--spacing-lg);
    }

    .btn--answer {
        max-width: 600px;
    }
}

@media (min-width: 769px) {

    /* Desktop - ẩn bottom nav, hiện sidebar */
    body {
        padding-bottom: 0;
    }

    .bottom-nav {
        display: none;
    }

    .main-content {
        max-width: 800px;
        margin-left: auto;
        margin-right: auto;
    }
}