/* ============================================================
   NFA → DFA Subset Construction Visualizer
   Premium AI-Themed Design System
   ============================================================ */

/* ---------- CSS Custom Properties ---------- */
:root {
    --bg-primary: #0a0a1a;
    --bg-secondary: #0f0f2a;
    --bg-card: rgba(16, 16, 42, 0.7);
    --bg-card-hover: rgba(22, 22, 55, 0.85);
    --bg-glass: rgba(255, 255, 255, 0.03);

    --text-primary: #e8e8f0;
    --text-secondary: #9898b8;
    --text-muted: #5a5a80;
    --text-accent: #a5b4fc;

    --accent-1: #6366f1;            /* Indigo */
    --accent-2: #818cf8;            /* Light Indigo */
    --accent-3: #06b6d4;            /* Cyan */
    --accent-4: #22d3ee;            /* Light Cyan */
    --accent-5: #f472b6;            /* Pink */
    --accent-6: #a78bfa;            /* Violet */

    --gradient-main: linear-gradient(135deg, #6366f1 0%, #06b6d4 100%);
    --gradient-alt: linear-gradient(135deg, #f472b6 0%, #818cf8 50%, #06b6d4 100%);
    --gradient-glow: linear-gradient(135deg, rgba(99,102,241,0.15) 0%, rgba(6,182,212,0.08) 100%);

    --border-color: rgba(99, 102, 241, 0.15);
    --border-glow: rgba(99, 102, 241, 0.35);

    --shadow-sm: 0 2px 8px rgba(0,0,0,0.3);
    --shadow-md: 0 8px 32px rgba(0,0,0,0.4);
    --shadow-lg: 0 16px 64px rgba(0,0,0,0.5);
    --shadow-glow: 0 0 30px rgba(99,102,241,0.15);

    --radius-sm: 8px;
    --radius-md: 14px;
    --radius-lg: 20px;
    --radius-xl: 28px;

    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

    --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-med: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-sans);
    background: linear-gradient(-45deg, #0f0c29, #302b63, #24243e, #0a0a1a);
    background-size: 400% 400%;
    animation: gradientBG 15s ease infinite;
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}

@keyframes gradientBG {
    0% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
    100% { background-position: 0% 50%; }
}

/* ---------- Particle & Neural Canvas ---------- */
#particle-canvas,
#neural-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: none;
    z-index: 0;
}

#neural-canvas {
    opacity: 0.35;
}

/* ---------- Header ---------- */
#app-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background: rgba(10, 10, 26, 0.82);
    backdrop-filter: blur(24px) saturate(1.4);
    -webkit-backdrop-filter: blur(24px) saturate(1.4);
    border-bottom: 1px solid var(--border-color);
}

.header-glow {
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 60%;
    height: 1px;
    background: var(--gradient-main);
    filter: blur(1px);
}

.header-content {
    max-width: 1400px;
    margin: 0 auto;
    padding: 12px 32px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 24px;
}

.logo-section {
    display: flex;
    align-items: center;
    gap: 14px;
}

.logo-icon {
    width: 44px;
    height: 44px;
    animation: logoPulse 3s ease-in-out infinite;
}

@keyframes logoPulse {
    0%, 100% { filter: drop-shadow(0 0 6px rgba(99,102,241,0.4)); }
    50% { filter: drop-shadow(0 0 16px rgba(6,182,212,0.6)); }
}

.logo-icon svg {
    width: 100%;
    height: 100%;
}

.logo-text h1 {
    font-size: 1.3rem;
    font-weight: 800;
    background: var(--gradient-main);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.02em;
}

.logo-text .subtitle {
    font-size: 0.7rem;
    color: var(--text-muted);
    letter-spacing: 0.08em;
    text-transform: uppercase;
    font-weight: 500;
}

.student-badge {
    display: flex;
    align-items: center;
    gap: 10px;
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 6px 16px;
}

.student-name {
    font-size: 0.85rem;
    font-weight: 700;
    background: var(--gradient-main);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.student-roll {
    font-family: var(--font-mono);
    font-size: 0.72rem;
    font-weight: 600;
    color: var(--text-muted);
    background: rgba(99,102,241,0.1);
    border: 1px solid rgba(99,102,241,0.2);
    padding: 2px 8px;
    border-radius: 4px;
}

.header-nav {
    display: flex;
    gap: 4px;
    background: rgba(255,255,255,0.03);
    border-radius: var(--radius-lg);
    padding: 4px;
    border: 1px solid var(--border-color);
}

.nav-btn {
    font-family: var(--font-sans);
    font-size: 0.82rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: transparent;
    border: none;
    padding: 8px 18px;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 6px;
    white-space: nowrap;
}

.nav-btn:hover {
    color: var(--text-primary);
    background: rgba(99,102,241,0.1);
}

.nav-btn.active {
    color: #fff;
    background: var(--gradient-main);
    box-shadow: 0 2px 12px rgba(99,102,241,0.35);
}

.nav-icon {
    font-size: 1rem;
}

/* ---------- Main Content ---------- */
#main-content {
    position: relative;
    z-index: 1;
    max-width: 1400px;
    margin: 0 auto;
    padding: 32px;
}

.content-section {
    display: none;
    animation: sectionFadeIn 0.5s ease forwards;
}

.content-section.active {
    display: block;
}

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

/* ---------- Section Headers ---------- */
.section-header {
    margin-bottom: 36px;
}

.section-title {
    font-size: 1.8rem;
    font-weight: 800;
    letter-spacing: -0.03em;
    display: flex;
    align-items: center;
    gap: 14px;
}

.title-accent {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--accent-3);
    background: rgba(6,182,212,0.1);
    border: 1px solid rgba(6,182,212,0.25);
    padding: 4px 10px;
    border-radius: var(--radius-sm);
}

.section-desc {
    color: var(--text-secondary);
    font-size: 0.95rem;
    margin-top: 8px;
    max-width: 600px;
}

/* ---------- Input Cards Grid ---------- */
.input-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 20px;
    margin-bottom: 24px;
}

.input-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    transition: var(--transition-med);
    position: relative;
    overflow: hidden;
}

.input-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient-main);
    opacity: 0;
    transition: var(--transition-med);
}

.input-card:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-glow);
    box-shadow: var(--shadow-glow);
}

.input-card:hover::before {
    opacity: 1;
}

.input-card.wide {
    grid-column: 1 / -1;
}

.card-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 18px;
}

.card-header h3 {
    font-size: 1.05rem;
    font-weight: 700;
    color: var(--text-primary);
}

.card-icon {
    width: 38px;
    height: 38px;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: var(--font-mono);
    font-weight: 700;
    font-size: 1.1rem;
}

.states-icon {
    background: rgba(99,102,241,0.15);
    color: var(--accent-2);
    border: 1px solid rgba(99,102,241,0.3);
}

.alphabet-icon {
    background: rgba(6,182,212,0.15);
    color: var(--accent-4);
    border: 1px solid rgba(6,182,212,0.3);
}

/* ---------- Form Elements ---------- */
.input-label {
    display: block;
    font-size: 0.78rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: 6px;
}

.text-input,
.select-input {
    width: 100%;
    font-family: var(--font-mono);
    font-size: 0.88rem;
    color: var(--text-primary);
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 10px 14px;
    outline: none;
    transition: var(--transition-fast);
}

.text-input:focus,
.select-input:focus {
    border-color: var(--accent-1);
    box-shadow: 0 0 0 3px rgba(99,102,241,0.15);
    background: rgba(255,255,255,0.06);
}

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

.select-input {
    appearance: none;
    cursor: pointer;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='12' viewBox='0 0 12 12'%3E%3Cpath d='M3 5l3 3 3-3' stroke='%239898b8' stroke-width='1.5' fill='none'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 36px;
}

.select-input option {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

/* Epsilon Toggle */
.epsilon-toggle {
    margin-top: 16px;
}

.toggle-label {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 0.85rem;
    color: var(--text-secondary);
    cursor: pointer;
}

.toggle-label input[type="checkbox"] {
    display: none;
}

.toggle-slider {
    width: 40px;
    height: 22px;
    background: rgba(255,255,255,0.1);
    border-radius: 11px;
    position: relative;
    transition: var(--transition-fast);
    flex-shrink: 0;
}

.toggle-slider::after {
    content: '';
    position: absolute;
    top: 3px;
    left: 3px;
    width: 16px;
    height: 16px;
    background: var(--text-secondary);
    border-radius: 50%;
    transition: var(--transition-fast);
}

.toggle-label input:checked + .toggle-slider {
    background: var(--accent-1);
}

.toggle-label input:checked + .toggle-slider::after {
    left: 21px;
    background: #fff;
}

/* ---------- Transition Table ---------- */
.transition-table-wrapper {
    overflow-x: auto;
}

.transition-input-table {
    width: 100%;
    border-collapse: collapse;
}

.transition-input-table th {
    text-align: left;
    font-size: 0.72rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
    padding: 8px 12px;
    border-bottom: 1px solid var(--border-color);
}

.transition-input-table td {
    padding: 6px 8px;
    border-bottom: 1px solid rgba(99,102,241,0.06);
}

.transition-input-table .text-input,
.transition-input-table .select-input {
    font-size: 0.82rem;
    padding: 8px 10px;
}

.btn-delete-row {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 1.1rem;
    padding: 4px 8px;
    border-radius: var(--radius-sm);
    transition: var(--transition-fast);
}

.btn-delete-row:hover {
    color: #ef4444;
    background: rgba(239,68,68,0.1);
}

.btn-add-transition {
    font-family: var(--font-sans);
    font-size: 0.8rem;
    font-weight: 600;
    color: var(--accent-3);
    background: rgba(6,182,212,0.1);
    border: 1px solid rgba(6,182,212,0.25);
    border-radius: var(--radius-sm);
    padding: 6px 14px;
    cursor: pointer;
    transition: var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 4px;
}

.btn-add-transition:hover {
    background: rgba(6,182,212,0.2);
    border-color: var(--accent-3);
}

.hint-text {
    font-size: 0.75rem;
    color: var(--text-muted);
    margin-top: 10px;
    font-style: italic;
}

/* ---------- Presets Bar ---------- */
.presets-bar {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 28px;
    flex-wrap: wrap;
}

.presets-label {
    font-size: 0.82rem;
    color: var(--text-muted);
    font-weight: 500;
}

.preset-btn {
    font-family: var(--font-sans);
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 6px 16px;
    cursor: pointer;
    transition: var(--transition-fast);
}

.preset-btn:hover {
    color: var(--accent-2);
    border-color: var(--accent-1);
    background: rgba(99,102,241,0.08);
}

/* ---------- Action Bar ---------- */
.action-bar {
    display: flex;
    justify-content: center;
}

.btn-primary {
    font-family: var(--font-sans);
    font-size: 1rem;
    font-weight: 700;
    color: #fff;
    background: var(--gradient-main);
    border: none;
    border-radius: var(--radius-md);
    padding: 14px 36px;
    cursor: pointer;
    position: relative;
    overflow: hidden;
    transition: var(--transition-med);
    display: flex;
    align-items: center;
    gap: 10px;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 30px rgba(99,102,241,0.4);
}

.btn-primary:active {
    transform: translateY(0);
}

.btn-icon {
    font-size: 1.2rem;
}

.btn-shimmer {
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255,255,255,0.15), transparent);
    animation: shimmer 3s infinite;
}

@keyframes shimmer {
    0% { left: -100%; }
    100% { left: 200%; }
}

/* ---------- Algorithm Section ---------- */
.algo-layout {
    display: grid;
    grid-template-columns: 1fr 1.3fr;
    gap: 20px;
}

.algo-steps-panel,
.dfa-table-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 20px;
    max-height: 600px;
    display: flex;
    flex-direction: column;
}

.algo-steps-panel h3,
.dfa-table-panel h3 {
    font-size: 1rem;
    font-weight: 700;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.steps-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 16px;
}

.steps-header h3 {
    margin-bottom: 0;
}

.step-controls {
    display: flex;
    align-items: center;
    gap: 6px;
}

.step-btn {
    font-family: var(--font-sans);
    font-size: 0.8rem;
    color: var(--text-secondary);
    background: rgba(255,255,255,0.05);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-sm);
    padding: 5px 10px;
    cursor: pointer;
    transition: var(--transition-fast);
}

.step-btn:hover:not(:disabled) {
    color: var(--accent-2);
    border-color: var(--accent-1);
    background: rgba(99,102,241,0.1);
}

.step-btn:disabled {
    opacity: 0.3;
    cursor: not-allowed;
}

.step-counter {
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-muted);
    padding: 0 6px;
}

.steps-list {
    flex: 1;
    overflow-y: auto;
    padding-right: 4px;
}

.steps-list::-webkit-scrollbar {
    width: 5px;
}
.steps-list::-webkit-scrollbar-track {
    background: transparent;
}
.steps-list::-webkit-scrollbar-thumb {
    background: var(--border-color);
    border-radius: 3px;
}

.empty-state {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 200px;
    color: var(--text-muted);
    font-size: 0.88rem;
    text-align: center;
}

/* Step Items */
.step-item {
    background: rgba(255,255,255,0.02);
    border: 1px solid rgba(99,102,241,0.08);
    border-radius: var(--radius-md);
    padding: 14px 16px;
    margin-bottom: 8px;
    transition: var(--transition-fast);
    opacity: 0.5;
    cursor: pointer;
}

.step-item.active {
    opacity: 1;
    border-color: var(--accent-1);
    background: rgba(99,102,241,0.06);
    box-shadow: 0 0 20px rgba(99,102,241,0.1);
}

.step-item.completed {
    opacity: 0.85;
    border-color: rgba(34,197,94,0.2);
}

.step-item:hover {
    opacity: 1;
}

.step-number {
    font-family: var(--font-mono);
    font-size: 0.7rem;
    font-weight: 700;
    color: var(--accent-3);
    margin-bottom: 4px;
}

.step-title {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.step-detail {
    font-size: 0.78rem;
    color: var(--text-secondary);
    font-family: var(--font-mono);
    line-height: 1.5;
}

.step-detail .state-set {
    display: inline-block;
    background: rgba(99,102,241,0.12);
    color: var(--accent-2);
    padding: 1px 7px;
    border-radius: 4px;
    font-weight: 600;
    margin: 1px 2px;
}

.step-detail .arrow {
    color: var(--accent-3);
    margin: 0 4px;
}

/* ---------- DFA Table ---------- */
.dfa-table-wrapper {
    flex: 1;
    overflow: auto;
}

.dfa-result-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.82rem;
}

.dfa-result-table th {
    font-weight: 700;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    font-size: 0.72rem;
    padding: 10px 14px;
    border-bottom: 2px solid var(--border-color);
    text-align: left;
    position: sticky;
    top: 0;
    background: var(--bg-card);
}

.dfa-result-table td {
    padding: 10px 14px;
    border-bottom: 1px solid rgba(99,102,241,0.06);
    font-family: var(--font-mono);
    font-size: 0.8rem;
    color: var(--text-primary);
    transition: var(--transition-fast);
}

.dfa-result-table tr.highlight {
    background: rgba(99,102,241,0.08);
}

.dfa-result-table tr.highlight td {
    color: var(--accent-2);
}

.dfa-state-cell {
    display: flex;
    align-items: center;
    gap: 6px;
}

.state-badge {
    display: inline-block;
    padding: 2px 8px;
    border-radius: 4px;
    font-weight: 600;
    font-size: 0.78rem;
}

.state-badge.start {
    background: rgba(99,102,241,0.15);
    color: var(--accent-2);
    border: 1px solid rgba(99,102,241,0.3);
}

.state-badge.accept {
    background: rgba(34,197,94,0.15);
    color: #4ade80;
    border: 1px solid rgba(34,197,94,0.3);
}

.state-badge.dead {
    background: rgba(239,68,68,0.1);
    color: #f87171;
    border: 1px solid rgba(239,68,68,0.2);
}

/* DFA Legend */
.dfa-legend {
    display: flex;
    gap: 18px;
    margin-top: 14px;
    padding-top: 12px;
    border-top: 1px solid var(--border-color);
}

.legend-item {
    font-size: 0.72rem;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 5px;
}

.legend-dot {
    width: 10px;
    height: 10px;
    border-radius: 50%;
}

.legend-dot.start { background: var(--accent-1); }
.legend-dot.accept { background: #22c55e; }
.legend-dot.current { background: var(--accent-4); box-shadow: 0 0 6px var(--accent-4); }
.legend-dot.dead { background: #ef4444; }

/* ---------- Visualization Section ---------- */
.viz-container {
    display: grid;
    grid-template-columns: 1fr auto 1fr;
    gap: 0;
    align-items: stretch;
}

.viz-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.viz-panel-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 20px;
    border-bottom: 1px solid var(--border-color);
}

.viz-panel-header h3 {
    font-size: 0.95rem;
    font-weight: 700;
}

.viz-controls {
    display: flex;
    gap: 4px;
}

.viz-btn {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    color: var(--text-secondary);
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    width: 30px;
    height: 30px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: var(--transition-fast);
}

.viz-btn:hover {
    color: var(--accent-2);
    border-color: var(--accent-1);
    background: rgba(99,102,241,0.1);
}

.viz-panel canvas {
    flex: 1;
    width: 100%;
    display: block;
    cursor: grab;
}

.viz-panel canvas:active {
    cursor: grabbing;
}

.viz-divider {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 0 14px;
    gap: 8px;
}

.divider-arrow {
    font-size: 1.4rem;
    background: var(--gradient-main);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    animation: arrowPulse 2s ease-in-out infinite;
}

@keyframes arrowPulse {
    0%, 100% { opacity: 0.4; }
    50% { opacity: 1; }
}

.divider-label {
    font-size: 0.68rem;
    color: var(--text-muted);
    text-align: center;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.06em;
}

/* ---------- String Test Panel ---------- */
.string-test-panel {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    margin-top: 24px;
}

.string-test-panel h3 {
    font-size: 1rem;
    font-weight: 700;
    margin-bottom: 14px;
}

.test-input-row {
    display: flex;
    gap: 10px;
}

.test-input-row .text-input {
    flex: 1;
}

.btn-test {
    padding: 10px 24px;
    font-size: 0.88rem;
    white-space: nowrap;
}

.test-result {
    margin-top: 14px;
    font-family: var(--font-mono);
    font-size: 0.88rem;
    line-height: 1.7;
    min-height: 0;
}

.test-result.accepted {
    color: #4ade80;
}

.test-result.rejected {
    color: #f87171;
}

.test-result .path-step {
    display: inline-block;
    background: rgba(99,102,241,0.12);
    color: var(--accent-2);
    padding: 2px 8px;
    border-radius: 4px;
    margin: 0 2px;
    font-weight: 600;
}

.test-result .path-arrow {
    color: var(--text-muted);
    margin: 0 4px;
}

/* ---------- Toast Notifications ---------- */
#toast-container {
    position: fixed;
    bottom: 24px;
    right: 24px;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.toast {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    color: var(--text-primary);
    background: rgba(16, 16, 42, 0.92);
    backdrop-filter: blur(16px);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 12px 20px;
    box-shadow: var(--shadow-md);
    animation: toastSlideIn 0.3s ease;
    max-width: 360px;
}

.toast.error {
    border-color: rgba(239,68,68,0.4);
    color: #fca5a5;
}

.toast.success {
    border-color: rgba(34,197,94,0.4);
    color: #86efac;
}

@keyframes toastSlideIn {
    from { opacity: 0; transform: translateX(40px); }
    to { opacity: 1; transform: translateX(0); }
}

@keyframes toastSlideOut {
    from { opacity: 1; transform: translateX(0); }
    to { opacity: 0; transform: translateX(40px); }
}

/* ---------- Language Input Section ---------- */
.lang-mode-toggle {
    display: flex;
    gap: 4px;
    background: rgba(255,255,255,0.03);
    border-radius: var(--radius-md);
    padding: 4px;
    border: 1px solid var(--border-color);
    width: fit-content;
    margin-bottom: 20px;
}

.mode-btn {
    font-family: var(--font-sans);
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    background: transparent;
    border: none;
    padding: 10px 22px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition-fast);
    display: flex;
    align-items: center;
    gap: 8px;
}

.mode-btn:hover {
    color: var(--text-primary);
    background: rgba(99,102,241,0.08);
}

.mode-btn.active {
    color: #fff;
    background: var(--gradient-alt);
    box-shadow: 0 2px 16px rgba(244,114,182,0.25);
}

.mode-icon {
    font-size: 1rem;
}

.lang-input-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    position: relative;
    overflow: hidden;
    transition: var(--transition-med);
}

.lang-input-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
    background: var(--gradient-alt);
    opacity: 0.6;
}

.lang-input-card:hover {
    border-color: var(--border-glow);
    box-shadow: var(--shadow-glow);
}

.lang-input-card.hidden {
    display: none;
}

.lang-input-row {
    display: flex;
    align-items: center;
    gap: 14px;
}

.lang-input-icon {
    width: 42px;
    height: 42px;
    border-radius: var(--radius-sm);
    background: rgba(244,114,182,0.12);
    border: 1px solid rgba(244,114,182,0.25);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    color: var(--accent-5);
    flex-shrink: 0;
    animation: iconGlow 3s ease-in-out infinite;
}

@keyframes iconGlow {
    0%, 100% { box-shadow: 0 0 8px rgba(244,114,182,0.15); }
    50% { box-shadow: 0 0 20px rgba(244,114,182,0.3); }
}

.lang-text-input {
    flex: 1;
    font-size: 1rem !important;
    padding: 14px 18px !important;
    font-family: var(--font-sans) !important;
    font-weight: 500;
}

.lang-examples {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
    margin-top: 16px;
}

.lang-examples-label {
    font-size: 0.78rem;
    color: var(--text-muted);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.lang-chip,
.regex-chip {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    font-weight: 500;
    color: var(--text-secondary);
    background: rgba(255,255,255,0.04);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    padding: 5px 14px;
    cursor: pointer;
    transition: var(--transition-fast);
    white-space: nowrap;
}

.lang-chip:hover,
.regex-chip:hover {
    color: var(--accent-5);
    border-color: rgba(244,114,182,0.4);
    background: rgba(244,114,182,0.08);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(244,114,182,0.15);
}

.lang-chip.selected,
.regex-chip.selected {
    color: #fff;
    background: rgba(244,114,182,0.2);
    border-color: var(--accent-5);
}

/* Result Grid */
.lang-result-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
    margin-top: 24px;
    animation: sectionFadeIn 0.4s ease forwards;
}

.lang-result-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 20px;
    position: relative;
    overflow: hidden;
}

.lang-result-card::after {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 2px;
}

.pattern-card::after {
    background: linear-gradient(90deg, var(--accent-5), var(--accent-6));
}

.nfa-summary-card::after {
    background: linear-gradient(90deg, var(--accent-1), var(--accent-3));
}

.result-card-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 14px;
}

.result-card-header h3 {
    font-size: 0.9rem;
    font-weight: 700;
    color: var(--text-primary);
}

.result-icon {
    font-size: 1.1rem;
}

.result-card-body {
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.7;
}

.pattern-type {
    font-family: var(--font-mono);
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--accent-5);
    margin-bottom: 8px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.pattern-type .pt-badge {
    display: inline-block;
    font-size: 0.7rem;
    font-weight: 600;
    padding: 2px 10px;
    border-radius: 20px;
    background: rgba(244,114,182,0.12);
    border: 1px solid rgba(244,114,182,0.25);
    color: var(--accent-5);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.pattern-details {
    font-size: 0.82rem;
    color: var(--text-secondary);
}

.pattern-details .pd-row {
    display: flex;
    gap: 8px;
    margin-bottom: 4px;
}

.pattern-details .pd-label {
    color: var(--text-muted);
    font-weight: 600;
    min-width: 70px;
    font-size: 0.75rem;
    text-transform: uppercase;
}

.pattern-details .pd-value {
    font-family: var(--font-mono);
    color: var(--accent-2);
    font-weight: 500;
}

/* NFA Summary */
.nfa-summary-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 8px;
}

.nfa-summary-grid .nfa-s-item {
    background: rgba(255,255,255,0.03);
    border: 1px solid rgba(99,102,241,0.08);
    border-radius: var(--radius-sm);
    padding: 8px 12px;
}

.nfa-s-item .nfa-s-label {
    font-size: 0.68rem;
    font-weight: 700;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.06em;
    margin-bottom: 2px;
}

.nfa-s-item .nfa-s-value {
    font-family: var(--font-mono);
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--accent-4);
}

.btn-generate {
    background: var(--gradient-alt) !important;
}

.btn-generate:hover {
    box-shadow: 0 8px 30px rgba(244,114,182,0.35) !important;
}

code {
    font-family: var(--font-mono);
    font-size: 0.85em;
    background: rgba(99,102,241,0.12);
    color: var(--accent-2);
    padding: 1px 6px;
    border-radius: 4px;
}

/* ---------- Responsive ---------- */
@media (max-width: 1024px) {
    .header-content {
        flex-direction: column;
        gap: 12px;
    }
    .input-grid {
        grid-template-columns: 1fr;
    }
    .input-card.wide {
        grid-column: 1;
    }
    .algo-layout {
        grid-template-columns: 1fr;
    }
    .viz-container {
        grid-template-columns: 1fr;
    }
    .viz-divider {
        flex-direction: row;
        padding: 14px 0;
    }
}

@media (max-width: 640px) {
    #main-content {
        padding: 16px;
    }
    .header-nav {
        width: 100%;
        justify-content: center;
    }
    .nav-btn {
        font-size: 0.75rem;
        padding: 6px 12px;
    }
    .section-title {
        font-size: 1.3rem;
    }
}

/* ---------- Custom Scrollbar ---------- */
::-webkit-scrollbar {
    width: 7px;
    height: 7px;
}
::-webkit-scrollbar-track {
    background: var(--bg-primary);
}
::-webkit-scrollbar-thumb {
    background: rgba(99,102,241,0.2);
    border-radius: 4px;
}
::-webkit-scrollbar-thumb:hover {
    background: rgba(99,102,241,0.35);
}