:root {
    /* Premium Aurora Palette */
    --primary: #a29bfe;
    /* Soft Purple */
    --accent: #00cec9;
    /* Cyan */
    --success: #55efc4;
    --danger: #ff7675;
    --warning: #ffeaa7;

    --bg-dark: #0f0c29;
    --text-main: #ffffff;
    --text-muted: rgba(255, 255, 255, 0.7);

    /* Glass Vars */
    --glass-bg: rgba(255, 255, 255, 0.05);
    /* Very subtle fill */
    --glass-border: rgba(255, 255, 255, 0.1);
    --glass-border-highlight: rgba(255, 255, 255, 0.2);
    --glass-shadow: 0 8px 32px 0 rgba(0, 0, 0, 0.37);
    --glass-blur: blur(16px);

    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;

    --font-main: 'Inter', sans-serif;
}

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

body {
    font-family: var(--font-main);
    background: #0f0c29;
    color: var(--text-main);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    overflow-x: hidden;
    position: relative;
}

/* Background "Aurora" Orbs */
/* Background Shapes */
.background-shapes {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    z-index: -1;
    overflow: hidden;
    pointer-events: none;
}

.shape {
    position: absolute;
    filter: blur(80px);
    border-radius: 50%;
    opacity: 0.6;
    animation: floating 20s infinite ease-in-out alternate;
}

.shape-1 {
    top: -10%;
    left: -10%;
    width: 60vw;
    height: 60vw;
    background: radial-gradient(circle, #4a148c, #311b92);
    animation-duration: 25s;
}

.shape-2 {
    bottom: -10%;
    right: -10%;
    width: 60vw;
    height: 60vw;
    background: radial-gradient(circle, #0d47a1, #1565c0);
    animation-duration: 30s;
    animation-delay: -5s;
}

.shape-3 {
    top: 30%;
    left: 40%;
    width: 35vw;
    height: 35vw;
    background: radial-gradient(circle, #006064, #00838f);
    animation-duration: 22s;
    animation-delay: -10s;
    opacity: 0.4;
}

@keyframes floating {
    0% {
        transform: translate(0, 0) scale(1);
    }

    50% {
        transform: translate(-30px, 50px) scale(1.1);
    }

    100% {
        transform: translate(0, 0) scale(1);
    }
}

/* Glass Panel (Main Container) */
.glass-panel {
    background: rgba(20, 20, 40, 0.6);
    box-shadow: var(--glass-shadow);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 24px;
    border: 1px solid var(--glass-border);
    border-top: 1px solid var(--glass-border-highlight);
}

/* Cards */
.glass-card {
    background: rgba(255, 255, 255, 0.03);
    border-radius: 16px;
    padding: var(--spacing-md);
    border: 1px solid var(--glass-border);
    transition: all 0.3s ease;
}

.glass-card:hover {
    background: rgba(255, 255, 255, 0.07);
    transform: translateY(-4px);
    border-color: var(--glass-border-highlight);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.2);
}

/* Typography */
h1,
h2,
h3 {
    color: var(--text-main);
    font-weight: 600;
    letter-spacing: -0.5px;
}

p {
    color: var(--text-muted);
}

/* Layout */
#app {
    width: 95vw;
    height: 90vh;
    display: grid;
    grid-template-columns: 260px 1fr;
    gap: var(--spacing-md);
    padding: var(--spacing-md);
}

aside {
    display: flex;
    flex-direction: column;
    padding: var(--spacing-md);
    gap: var(--spacing-sm);
}

/* Navigation */
.nav-item {
    padding: 1rem;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s;
    color: var(--text-muted);
    text-decoration: none;
    font-weight: 500;
    display: flex;
    align-items: center;
    gap: 12px;
}

.nav-item:hover {
    color: var(--text-main);
    background: rgba(255, 255, 255, 0.05);
}

.nav-item.active {
    background: linear-gradient(90deg, rgba(108, 92, 231, 0.2) 0%, rgba(108, 92, 231, 0) 100%);
    color: var(--primary);
    border-left: 3px solid var(--primary);
}

.nav-item svg {
    width: 20px;
    height: 20px;
}

/* Main Content */
main {
    padding: var(--spacing-lg);
    overflow-y: auto;
    position: relative;
    /* Custom Scrollbar for container */
    scrollbar-width: thin;
    scrollbar-color: rgba(255, 255, 255, 0.1) transparent;
}

/* Inputs & Forms */
input,
select,
textarea {
    width: 100%;
    padding: 1rem;
    border-radius: 12px;
    border: 1px solid var(--glass-border);
    background: rgba(0, 0, 0, 0.2);
    color: var(--text-main);
    font-size: 1rem;
    outline: none;
    transition: all 0.3s;
}

input:focus,
select:focus {
    border-color: var(--primary);
    background: rgba(0, 0, 0, 0.4);
    box-shadow: 0 0 0 2px rgba(162, 155, 254, 0.2);
}

/* Buttons */
button {
    background: linear-gradient(135deg, #6c5ce7, #a29bfe);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 12px;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: 0 4px 15px rgba(108, 92, 231, 0.3);
}

button:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(108, 92, 231, 0.4);
    filter: brightness(1.1);
}

button.secondary {
    background: rgba(255, 255, 255, 0.1);
    color: var(--text-main);
    box-shadow: none;
}

button.secondary:hover {
    background: rgba(255, 255, 255, 0.15);
}

button.icon-btn {
    padding: 0.5rem;
    background: transparent;
    box-shadow: none;
    color: var(--text-muted);
}

button.icon-btn:hover {
    color: var(--text-main);
    background: rgba(255, 255, 255, 0.1);
}

/* Tables */
.glass-table {
    width: 100%;
    border-collapse: collapse;
    margin-top: 1rem;
    color: var(--text-muted);
}

.glass-table th {
    text-align: left;
    padding: 1rem;
    color: var(--text-main);
    border-bottom: 1px solid var(--glass-border);
}

.glass-table td {
    padding: 1rem;
    border-bottom: 1px solid var(--glass-border);
}

.glass-table tr:hover td {
    background: rgba(255, 255, 255, 0.02);
    color: var(--text-main);
}

/* Badges */
.badge {
    background: rgba(108, 92, 231, 0.2);
    color: #a29bfe;
    padding: 2px 8px;
    border-radius: 6px;
    font-size: 0.8rem;
    border: 1px solid rgba(108, 92, 231, 0.3);
}

/* Stats */
.stat-value {
    font-size: 3rem;
    font-weight: 700;
    background: linear-gradient(to right, #ffffff, #a29bfe);
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

/* Diff */
.diff-result {
    background: rgba(0, 0, 0, 0.3);
    border: 1px solid var(--glass-border);
    color: var(--text-main);
    padding: 1rem;
}

.diff-add {
    background-color: rgba(46, 204, 113, 0.2);
    color: #2ecc71;
    border-radius: 2px;
    padding: 0 2px;
}

.diff-rem {
    background-color: rgba(231, 76, 60, 0.2);
    color: #e74c3c;
    border-radius: 2px;
    padding: 0 2px;
}

.success {
    color: var(--success);
}

.danger {
    color: var(--danger);
}

.warning {
    color: var(--warning);
}

/* Hidden */
.hidden {
    display: none !important;
}

/* SVG formatting in buttons/nav */
svg {
    vertical-align: middle;
}

/* MCQ Styles - Transparent Glass */
.mcq-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.5rem;
    margin-top: 2rem;
}

.mcq-btn {
    background: rgba(255, 255, 255, 0.02);
    border: 1px solid rgba(255, 255, 255, 0.15);
    color: var(--text-main);
    padding: 2.5rem;
    font-size: 1.3rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    text-align: center;
    border-radius: 16px;
    box-shadow: none;
    white-space: normal;
    word-break: break-word;
    position: relative;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 140px;
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
}

.key-hint {
    position: absolute;
    top: 12px;
    left: 12px;
    background: rgba(255, 255, 255, 0.1);
    border: 1px solid rgba(255, 255, 255, 0.2);
    width: 28px;
    height: 28px;
    border-radius: 50%;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-muted);
    font-weight: 600;
}

@media (max-width: 768px) {
    .key-hint {
        display: none;
    }
}

.mcq-btn:hover:not(:disabled) {
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(255, 255, 255, 0.3);
    transform: translateY(-4px);
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

.mcq-btn:disabled {
    cursor: default;
    opacity: 0.7;
    transform: none;
}

.mcq-btn.correct {
    background: rgba(46, 204, 113, 0.4);
    border-color: #2ecc71;
    color: #fff;
    box-shadow: 0 0 15px rgba(46, 204, 113, 0.3);
}

.mcq-btn.wrong {
    background: rgba(231, 76, 60, 0.4);
    border-color: #e74c3c;
    color: #fff;
}

@media (max-width: 768px) {
    .mcq-grid {
        grid-template-columns: 1fr;
    }

    .mcq-btn {
        padding: 1.5rem;
        min-height: auto;
    }
}

/* ─── Effects & Animations ─────────────────────────────────── */

/* Shake animation for wrong answers */
@keyframes fx-shake {

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

    10%,
    50%,
    90% {
        transform: translateX(-6px);
    }

    30%,
    70% {
        transform: translateX(6px);
    }
}

.fx-shake {
    animation: fx-shake 0.5s ease-in-out;
}

/* Streak banner */
.fx-streak-banner {
    position: fixed;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%) scale(0.3);
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.25rem;
    z-index: 9998;
    pointer-events: none;
    opacity: 0;
    transition: all 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.fx-streak-banner.fx-streak-show {
    opacity: 1;
    transform: translate(-50%, -50%) scale(1);
}

.fx-streak-number {
    font-size: 5rem;
    font-weight: 900;
    background: linear-gradient(135deg, #feca57, #ff6b6b, #ff9ff3);
    background-clip: text;
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    text-shadow: none;
    line-height: 1;
    filter: drop-shadow(0 0 20px rgba(255, 107, 107, 0.4));
}

.fx-streak-label {
    font-size: 1.5rem;
    font-weight: 600;
    color: rgba(255, 255, 255, 0.9);
    text-transform: uppercase;
    letter-spacing: 0.3em;
}

/* Correct answer card pulse */
@keyframes fx-correct-pulse {
    0% {
        box-shadow: 0 0 0 0 rgba(46, 204, 113, 0.4);
    }

    70% {
        box-shadow: 0 0 0 15px rgba(46, 204, 113, 0);
    }

    100% {
        box-shadow: 0 0 0 0 rgba(46, 204, 113, 0);
    }
}

.fx-correct-pulse {
    animation: fx-correct-pulse 0.8s ease-out;
}

/* Wrong answer card flash */
@keyframes fx-wrong-flash {
    0% {
        background-color: rgba(231, 76, 60, 0.15);
    }

    100% {
        background-color: transparent;
    }
}

.fx-wrong-flash {
    animation: fx-wrong-flash 0.8s ease-out;
}

/* Speedrun Timer */
.speedrun-timer {
    font-size: 1.25rem;
    font-weight: 700;
    font-family: monospace;
    color: var(--text-main);
    background: rgba(0, 0, 0, 0.2);
    padding: 0.25rem 0.75rem;
    border-radius: 8px;
    border: 1px solid var(--glass-border);
    transition: all 0.3s ease;
}

@keyframes fx-timer-pulse {
    0% {
        color: var(--danger);
        transform: scale(1);
    }

    50% {
        color: #ff9ff3;
        transform: scale(1.1);
    }

    100% {
        color: var(--danger);
        transform: scale(1);
    }
}

.timer-hurry {
    animation: fx-timer-pulse 1s infinite alternate;
    border-color: var(--danger);
}

/* Streak Text Shine */
@keyframes fx-streak-shine {
    0% {
        background-position: -200% center;
    }

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

.fx-streak-text {
    background: linear-gradient(120deg, #ff9f43 20%, #ff6b6b 40%, #ff9f43 60%);
    background-size: 200% auto;
    color: transparent;
    -webkit-background-clip: text;
    background-clip: text;
    animation: fx-streak-shine 3s linear infinite;
    display: inline-block;
}

/* ── SRS Progress Bars ──────────────────────────────────── */

.srs-progress-wrap {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.srs-progress-label {
    font-size: 0.8rem;
    font-weight: 600;
    min-width: 36px;
    text-align: right;
    color: var(--text-muted);
}

.srs-progress-track {
    flex: 1;
    background: rgba(255, 255, 255, 0.12);
    border-radius: 100px;
    overflow: hidden;
    border: 1px solid rgba(255, 255, 255, 0.08);
    min-height: 8px;
}

.srs-progress-fill {
    border-radius: 100px;
    transition: width 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    min-width: 0;
}

.srs-progress-fill::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(90deg,
            rgba(255, 255, 255, 0) 0%,
            rgba(255, 255, 255, 0.2) 50%,
            rgba(255, 255, 255, 0) 100%);
    border-radius: 100px;
}