:root {
    --bg: #030305;
    --surface: rgba(255, 255, 255, 0.025);
    --surface-hover: rgba(255, 255, 255, 0.05);
    --surface-active: rgba(255, 255, 255, 0.08);
    --surface-elevated: rgba(255, 255, 255, 0.04);
    --border: rgba(255, 255, 255, 0.06);
    --border-hover: rgba(255, 255, 255, 0.15);

    --text: #f8f8f8;
    --text-secondary: rgba(255, 255, 255, 0.55);
    --text-muted: rgba(255, 255, 255, 0.5);

    --accent: #a855f7;
    --accent-light: #c084fc;
    --accent-dark: #7c3aed;
    --accent-glow: rgba(168, 85, 247, 0.5);

    --success: #22c55e;
    --success-glow: rgba(34, 197, 94, 0.35);
    --error: #f43f5e;
    --error-glow: rgba(244, 63, 94, 0.35);
    --warning: #fbbf24;

    --radius-sm: 10px;
    --radius-md: 14px;
    --radius-lg: 20px;
    --radius-xl: 28px;

    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 8px 30px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 20px 60px rgba(0, 0, 0, 0.5);
}

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

html {
    font-size: 16px;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

body {
    font-family: 'Space Grotesk', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
    overflow-x: hidden;
    line-height: 1.5;
}

/* Premium Animated Background */
.background {
    position: fixed;
    inset: 0;
    z-index: 0;
    overflow: hidden;
}

.gradient-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(150px);
    opacity: 0.35;
    will-change: transform;
}

.orb-1 {
    width: 700px;
    height: 700px;
    background: radial-gradient(circle, #7c3aed 0%, transparent 70%);
    top: -300px;
    left: -200px;
    animation: orbit1 40s ease-in-out infinite;
}

.orb-2 {
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, #6366f1 0%, transparent 70%);
    bottom: -200px;
    right: -150px;
    animation: orbit2 45s ease-in-out infinite;
}

.orb-3 {
    width: 400px;
    height: 400px;
    background: radial-gradient(circle, #8b5cf6 0%, transparent 70%);
    top: 40%;
    left: 40%;
    animation: orbit3 35s ease-in-out infinite;
}

@keyframes orbit1 {
    0%, 100% { transform: translate(0, 0) scale(1); }
    25% { transform: translate(50px, 30px) scale(1.1); }
    50% { transform: translate(20px, -40px) scale(0.95); }
    75% { transform: translate(-30px, 20px) scale(1.05); }
}

@keyframes orbit2 {
    0%, 100% { transform: translate(0, 0) scale(1); }
    25% { transform: translate(-40px, -30px) scale(0.95); }
    50% { transform: translate(30px, 50px) scale(1.1); }
    75% { transform: translate(50px, -20px) scale(1); }
}

@keyframes orbit3 {
    0%, 100% { transform: translate(-50%, -50%) scale(1); }
    33% { transform: translate(-45%, -55%) scale(1.15); }
    66% { transform: translate(-55%, -45%) scale(0.9); }
}

.noise {
    position: absolute;
    inset: 0;
    background-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 512 512' xmlns='http://www.w3.org/2000/svg'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.7' numOctaves='4'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
    opacity: 0.018;
    pointer-events: none;
}

/* App Container */
.app {
    position: relative;
    z-index: 1;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Navbar */
.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 2.5rem;
    border-bottom: 1px solid var(--border);
    backdrop-filter: blur(30px) saturate(150%);
    background: rgba(3, 3, 5, 0.75);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.logo-symbol {
    font-size: 2.5rem;
    font-weight: 200;
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-light) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo-text {
    display: flex;
    flex-direction: column;
    gap: 0.125rem;
}

.logo-title {
    font-size: 1.35rem;
    font-weight: 700;
    letter-spacing: -0.03em;
    background: linear-gradient(135deg, var(--text) 0%, var(--text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.logo-subtitle {
    font-size: 0.7rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.15em;
    font-weight: 500;
}

.nav-stats {
    display: flex;
    align-items: center;
    gap: 0;
    padding: 0.5rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-lg);
    backdrop-filter: blur(10px);
}

.nav-stat {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.125rem;
    padding: 0.5rem 1.25rem;
    border-radius: var(--radius-md);
    transition: background 0.2s ease;
}

.nav-stat:hover {
    background: var(--surface-hover);
}

.nav-stat-value {
    font-family: 'JetBrains Mono', monospace;
    font-size: 1.35rem;
    font-weight: 700;
    line-height: 1;
}

.nav-stat-label {
    font-size: 0.6rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    font-weight: 500;
}

.nav-stat-divider {
    width: 1px;
    height: 28px;
    background: linear-gradient(to bottom, transparent, var(--border), transparent);
}

.nav-stat.streak .nav-stat-value {
    background: linear-gradient(135deg, #fbbf24 0%, #f59e0b 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* Main Content */
.main-content {
    display: grid;
    grid-template-columns: 1fr 340px;
    gap: 2.5rem;
    padding: 2.5rem;
    flex: 1;
    max-width: 1440px;
    margin: 0 auto;
    width: 100%;
}

/* Practice Section */
.practice-section {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* Control Panel */
.control-panel {
    display: flex;
    gap: 2.5rem;
    flex-wrap: wrap;
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 0.625rem;
}

.control-label {
    font-size: 0.65rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.15em;
    font-weight: 600;
    padding-left: 0.375rem;
}

.segmented-control {
    display: flex;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    padding: 5px;
    position: relative;
}

.segment {
    display: flex;
    align-items: center;
    gap: 0.625rem;
    padding: 0.75rem 1.25rem;
    background: transparent;
    border: none;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    position: relative;
    z-index: 1;
}

.segment:hover {
    color: var(--text);
}

.segment:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.segment.active {
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
    color: white;
    box-shadow: 0 2px 10px var(--accent-glow);
}

.segment-icon {
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9rem;
    font-weight: 600;
    opacity: 0.9;
}

.pill-group {
    display: flex;
    gap: 0.5rem;
}

.pill {
    padding: 0.75rem 1.125rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-family: inherit;
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.pill:hover {
    border-color: var(--border-hover);
    color: var(--text);
    transform: translateY(-1px);
}

.pill:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.pill.active {
    background: var(--surface-active);
    border-color: var(--accent);
    color: var(--text);
    box-shadow: 0 0 0 1px var(--accent), 0 4px 12px rgba(168, 85, 247, 0.15);
}

.pill.extreme {
    color: var(--error);
}

.pill.extreme:hover {
    border-color: var(--error);
}

.pill.extreme.active {
    border-color: var(--error);
    box-shadow: 0 0 0 1px var(--error), 0 4px 15px var(--error-glow);
}

.pill.time {
    font-family: 'JetBrains Mono', monospace;
    min-width: 60px;
    text-align: center;
}

/* Problem Container */
.problem-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.75rem;
}

/* Timer */
.timer-display {
    position: relative;
    width: 130px;
    height: 130px;
}

.timer-svg {
    width: 100%;
    height: 100%;
    transform: rotate(-90deg);
}

.timer-track {
    fill: none;
    stroke: var(--border);
    stroke-width: 5;
}

.timer-fill {
    fill: none;
    stroke: url(#timer-gradient);
    stroke-width: 5;
    stroke-linecap: round;
    stroke-dasharray: 339.292;
    stroke-dashoffset: 0;
    transition: stroke-dashoffset 1s linear;
    filter: drop-shadow(0 0 12px var(--accent-glow));
}

.timer-fill.warning {
    stroke: var(--warning);
    filter: drop-shadow(0 0 12px rgba(251, 191, 36, 0.5));
}

.timer-fill.danger {
    stroke: var(--error);
    filter: drop-shadow(0 0 15px var(--error-glow));
    animation: pulse 0.6s ease-in-out infinite;
}

@keyframes pulse {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.7; transform: scale(1.02); }
}

.timer-inner {
    position: absolute;
    inset: 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}

.timer-number {
    font-family: 'JetBrains Mono', monospace;
    font-size: 2.25rem;
    font-weight: 700;
    line-height: 1;
    background: linear-gradient(180deg, var(--text) 0%, var(--text-secondary) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.timer-label {
    font-size: 0.55rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-weight: 500;
    margin-top: 0.25rem;
}

/* Problem Card */
.problem-card {
    width: 100%;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-xl);
    padding: 3rem 2.5rem;
    backdrop-filter: blur(20px);
    transition: all 0.3s ease;
    position: relative;
}

.problem-card:hover {
    border-color: var(--border-hover);
}

.problem-card.success {
    border-color: var(--success);
    box-shadow: 0 0 30px var(--success-glow);
}

.problem-card.error {
    border-color: var(--error);
    box-shadow: 0 0 30px var(--error-glow);
}

.problem-content {
    font-size: 1.6rem;
    text-align: center;
    min-height: 120px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    z-index: 1;
}

.empty-state {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.empty-icon {
    font-size: 3.5rem;
    opacity: 0.06;
    margin-bottom: 0.5rem;
}

.empty-state p {
    font-size: 1.15rem;
    color: var(--text-secondary);
    font-weight: 500;
}

.empty-state span {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.problem-source {
    margin-top: 1rem;
    font-size: 0.75rem;
    color: var(--text-muted);
    font-style: italic;
}

/* Countdown */
.countdown {
    font-family: 'JetBrains Mono', monospace;
    font-size: 4rem;
    font-weight: 700;
    color: var(--accent);
    animation: countPop 0.7s cubic-bezier(0.4, 0, 0.2, 1);
}

.countdown.go {
    font-size: 3rem;
    color: var(--success);
    animation: goPop 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes countPop {
    0% {
        transform: scale(0.3);
        opacity: 0;
    }
    50% {
        transform: scale(1.2);
        opacity: 1;
    }
    100% {
        transform: scale(1);
        opacity: 1;
    }
}

@keyframes goPop {
    0% {
        transform: scale(0.5);
        opacity: 0;
    }
    60% {
        transform: scale(1.3);
    }
    100% {
        transform: scale(1);
        opacity: 1;
    }
}

.problem-author {
    margin-top: 0.75rem;
    font-size: 0.7rem;
    color: var(--accent-light);
    opacity: 0.7;
}

/* Hint */
.hint-display {
    padding: 0.875rem 1.5rem;
    background: linear-gradient(135deg, rgba(168, 85, 247, 0.12) 0%, rgba(168, 85, 247, 0.05) 100%);
    border: 1px solid rgba(168, 85, 247, 0.25);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    animation: slideDown 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes slideDown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
}

.hint-label {
    color: var(--accent-light);
    font-weight: 600;
    margin-right: 0.625rem;
}

#hint-text {
    color: var(--text-secondary);
}

/* Answer Card */
.answer-card {
    width: 100%;
    background: linear-gradient(135deg, rgba(34, 197, 94, 0.1) 0%, rgba(34, 197, 94, 0.03) 100%);
    border: 1px solid rgba(34, 197, 94, 0.25);
    border-radius: var(--radius-lg);
    padding: 1.75rem 2rem;
    animation: revealUp 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes revealUp {
    from { opacity: 0; transform: translateY(20px) scale(0.98); }
    to { opacity: 1; transform: translateY(0) scale(1); }
}

.answer-header {
    margin-bottom: 1rem;
}

.answer-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.375rem 1rem;
    background: rgba(34, 197, 94, 0.15);
    border-radius: 100px;
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--success);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.answer-content {
    font-size: 1.3rem;
    text-align: center;
}

/* Feedback Buttons */
.feedback-buttons {
    display: flex;
    gap: 1rem;
    width: 100%;
    animation: revealUp 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    animation-delay: 0.1s;
    animation-fill-mode: backwards;
}

.feedback-btn {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.875rem;
    padding: 1.125rem 1.75rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    color: var(--text);
    font-family: inherit;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.feedback-btn svg {
    width: 22px;
    height: 22px;
    stroke-width: 2.5;
}

.feedback-btn.success:hover {
    background: rgba(34, 197, 94, 0.1);
    border-color: var(--success);
    color: var(--success);
}

.feedback-btn.error:hover {
    background: rgba(244, 63, 94, 0.1);
    border-color: var(--error);
    color: var(--error);
}

.feedback-btn:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

/* Share Section */
.share-section {
    display: flex;
    gap: 0.75rem;
    justify-content: center;
    animation: revealUp 0.4s ease;
}

.share-btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem 1.25rem;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-family: inherit;
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
}

.share-btn:hover {
    border-color: var(--accent);
    color: var(--accent);
}

/* Action Bar */
.action-bar {
    display: flex;
    gap: 1rem;
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.625rem;
    padding: 1rem 1.75rem;
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.95rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

.btn svg {
    width: 20px;
    height: 20px;
}

.btn:disabled {
    opacity: 0.35;
    cursor: not-allowed;
    transform: none !important;
}

.btn:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.btn-primary {
    flex: 1;
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
    border: none;
    color: white;
    box-shadow: 0 2px 12px var(--accent-glow);
}

.btn-primary:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: 0 4px 20px var(--accent-glow);
}

.btn-primary:active:not(:disabled) {
    transform: translateY(0);
}

.btn-secondary {
    flex: 1;
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text-secondary);
}

.btn-secondary:hover:not(:disabled) {
    border-color: var(--accent);
    color: var(--accent);
    background: rgba(168, 85, 247, 0.08);
    transform: translateY(-2px);
}

.btn-ghost {
    background: transparent;
    border: 1px solid var(--border);
    color: var(--text-muted);
}

.btn-ghost:hover:not(:disabled) {
    border-color: var(--border-hover);
    color: var(--text-secondary);
    background: var(--surface);
}

/* Leaderboard */
.leaderboard-section {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-xl);
    padding: 1.5rem;
    height: fit-content;
    position: sticky;
    top: 90px;
    backdrop-filter: blur(20px);
}

.leaderboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.25rem;
}

.leaderboard-header h2 {
    font-size: 1.1rem;
    font-weight: 700;
    letter-spacing: -0.02em;
}

.btn-icon {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-muted);
    cursor: pointer;
    transition: all 0.2s ease;
}

.btn-icon:hover {
    border-color: var(--border-hover);
    color: var(--text);
    transform: rotate(180deg);
}

.btn-icon:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.btn-icon svg {
    width: 18px;
    height: 18px;
}

.leaderboard-submit {
    display: flex;
    gap: 0.625rem;
    margin-bottom: 1.25rem;
    padding-bottom: 1.25rem;
    border-bottom: 1px solid var(--border);
}

.leaderboard-submit input {
    flex: 1;
    padding: 0.75rem 1rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text);
    font-family: inherit;
    font-size: 0.875rem;
    transition: all 0.2s ease;
}

.leaderboard-submit input::placeholder {
    color: var(--text-muted);
}

.leaderboard-submit input:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(168, 85, 247, 0.15);
}

.btn-small {
    padding: 0.75rem 1.25rem;
    font-size: 0.8rem;
    background: linear-gradient(135deg, var(--accent) 0%, var(--accent-dark) 100%);
    border: none;
    color: white;
    font-weight: 700;
}

.btn-small:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 15px var(--accent-glow);
}

.leaderboard-list {
    display: flex;
    flex-direction: column;
    gap: 0.625rem;
    max-height: 450px;
    overflow-y: auto;
    padding-right: 0.5rem;
}

.leaderboard-empty {
    text-align: center;
    padding: 3rem 1rem;
}

.leaderboard-empty p {
    color: var(--text-secondary);
    margin-bottom: 0.375rem;
    font-weight: 500;
}

.leaderboard-empty span {
    font-size: 0.875rem;
    color: var(--text-muted);
}

.leaderboard-item {
    display: flex;
    align-items: center;
    gap: 0.875rem;
    padding: 0.875rem 1rem;
    background: var(--bg);
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
}

.leaderboard-item:hover {
    background: var(--surface);
    transform: translateX(4px);
}

.leaderboard-rank {
    width: 28px;
    height: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
    font-weight: 700;
    border-radius: 50%;
    background: var(--surface);
    flex-shrink: 0;
}

.leaderboard-item:nth-child(1) .leaderboard-rank {
    background: linear-gradient(135deg, #fcd34d 0%, #f59e0b 100%);
    color: #000;
    box-shadow: 0 2px 10px rgba(251, 191, 36, 0.4);
}

.leaderboard-item:nth-child(2) .leaderboard-rank {
    background: linear-gradient(135deg, #e5e7eb 0%, #9ca3af 100%);
    color: #000;
}

.leaderboard-item:nth-child(3) .leaderboard-rank {
    background: linear-gradient(135deg, #fbbf24 0%, #b45309 100%);
    color: #fff;
}

.leaderboard-name {
    flex: 1;
    font-size: 0.9rem;
    font-weight: 600;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.leaderboard-stats {
    display: flex;
    gap: 1.25rem;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.75rem;
}

.leaderboard-stat {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    gap: 0.125rem;
}

.leaderboard-stat-value {
    color: var(--accent-light);
    font-weight: 600;
}

.leaderboard-stat-label {
    color: var(--text-muted);
    font-size: 0.55rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

/* Toast Notifications */
.toast {
    position: fixed;
    bottom: 2rem;
    left: 50%;
    transform: translateX(-50%);
    display: flex;
    align-items: center;
    gap: 1rem;
    padding: 1rem 1.25rem;
    background: var(--surface-elevated);
    border: 1px solid var(--border);
    border-radius: var(--radius-md);
    backdrop-filter: blur(20px);
    box-shadow: var(--shadow-lg);
    z-index: 1100;
    animation: toastIn 0.3s ease;
}

@keyframes toastIn {
    from {
        opacity: 0;
        transform: translateX(-50%) translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateX(-50%) translateY(0);
    }
}

.toast-fade {
    opacity: 0;
    transform: translateX(-50%) translateY(20px);
    transition: all 0.3s ease;
}

.toast-message {
    font-size: 0.9rem;
    color: var(--text);
}

.toast-close {
    background: none;
    border: none;
    color: var(--text-muted);
    font-size: 1.25rem;
    cursor: pointer;
    padding: 0;
    line-height: 1;
}

.toast-close:hover {
    color: var(--text);
}

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

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

.toast-error {
    border-color: var(--error);
}

.toast-error .toast-message {
    color: var(--error);
}

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

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

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

/* MathJax */
.MathJax {
    font-size: 1.15em !important;
}

/* Scrollbar */
::-webkit-scrollbar {
    width: 6px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: var(--border);
    border-radius: 3px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--border-hover);
}

/* Selection */
::selection {
    background: rgba(168, 85, 247, 0.3);
}

/* Community pill special style */
.pill.community-pill {
    background: linear-gradient(135deg, rgba(236, 72, 153, 0.1) 0%, rgba(168, 85, 247, 0.1) 100%);
    border-color: rgba(236, 72, 153, 0.3);
    color: #ec4899;
}

.pill.community-pill:hover {
    border-color: #ec4899;
}

.pill.community-pill.active {
    background: linear-gradient(135deg, #ec4899 0%, #a855f7 100%);
    border-color: transparent;
    color: white;
    box-shadow: 0 4px 15px rgba(236, 72, 153, 0.4);
}

/* Modal */
.modal {
    position: fixed;
    inset: 0;
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 1rem;
}

.modal-backdrop {
    position: absolute;
    inset: 0;
    background: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(8px);
}

.modal-content {
    position: relative;
    width: 100%;
    max-width: 500px;
    background: linear-gradient(135deg, var(--surface-elevated) 0%, var(--bg) 100%);
    border: 1px solid var(--border);
    border-radius: var(--radius-xl);
    animation: modalIn 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes modalIn {
    from {
        opacity: 0;
        transform: scale(0.95) translateY(20px);
    }
    to {
        opacity: 1;
        transform: scale(1) translateY(0);
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1.5rem 1.75rem;
    border-bottom: 1px solid var(--border);
}

.modal-header h3 {
    font-size: 1.1rem;
    font-weight: 700;
}

.modal-close {
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: transparent;
    border: none;
    color: var(--text-muted);
    font-size: 1.5rem;
    cursor: pointer;
    border-radius: var(--radius-sm);
    transition: all 0.2s ease;
}

.modal-close:hover {
    background: var(--surface);
    color: var(--text);
}

.modal-close:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.modal-body {
    padding: 1.5rem 1.75rem;
}

.modal-desc {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
}

.form-group {
    margin-bottom: 1.25rem;
}

.form-group label {
    display: block;
    font-size: 0.7rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.1em;
    margin-bottom: 0.5rem;
}

.form-group input,
.form-group textarea,
.form-group select {
    width: 100%;
    padding: 0.75rem 1rem;
    background: var(--bg);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text);
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.875rem;
    transition: all 0.2s ease;
    resize: vertical;
}

.form-group input::placeholder,
.form-group textarea::placeholder {
    color: var(--text-muted);
    font-family: 'JetBrains Mono', monospace;
}

.form-group input:focus,
.form-group textarea:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(168, 85, 247, 0.15);
}

.form-group select {
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 24 24' fill='none' stroke='%23666' stroke-width='2'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 1rem center;
    padding-right: 2.5rem;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.modal-footer {
    display: flex;
    gap: 1rem;
    padding: 1.25rem 1.75rem;
    border-top: 1px solid var(--border);
}

.modal-footer .btn {
    flex: 1;
}

/* Contribute Button */
.contribute-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    width: 100%;
    padding: 0.875rem 1rem;
    margin-top: 1rem;
    background: transparent;
    border: 1px dashed var(--border);
    border-radius: var(--radius-md);
    color: var(--text-muted);
    font-family: inherit;
    font-size: 0.8rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s ease;
}

.contribute-btn:hover {
    border-color: var(--accent);
    border-style: solid;
    color: var(--accent);
    background: rgba(168, 85, 247, 0.05);
}

.contribute-btn:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
}

.contribute-btn svg {
    width: 16px;
    height: 16px;
    opacity: 0.7;
}

.contribute-btn:hover svg {
    opacity: 1;
}

/* Week Badge */
.leaderboard-title {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.week-badge {
    font-size: 0.65rem;
    font-family: 'JetBrains Mono', monospace;
    color: var(--accent-light);
    opacity: 0.8;
    letter-spacing: 0.02em;
}

/* Responsive */
@media (max-width: 1100px) {
    .main-content {
        grid-template-columns: 1fr;
    }

    .leaderboard-section {
        position: static;
    }
}

@media (max-width: 768px) {
    .navbar {
        flex-direction: column;
        gap: 1.25rem;
        padding: 1.25rem;
    }

    .main-content {
        padding: 1.25rem;
    }

    .control-panel {
        flex-direction: column;
        gap: 1.25rem;
    }

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

    .action-bar {
        flex-direction: column;
    }

    .feedback-buttons {
        flex-direction: column;
    }

    .problem-content {
        font-size: 1.25rem;
    }

    .problem-card {
        padding: 2.5rem 1.5rem;
    }
}

/* Reduced Motion */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
        scroll-behavior: auto !important;
    }

    .gradient-orb {
        animation: none;
    }

    .timer-fill {
        transition: none;
    }

    .btn-icon:hover {
        transform: none;
    }
}