/* ═══════════════════════════════════════════════════════════
   ShadowChat — Global Design System
   ═══════════════════════════════════════════════════════════ */

/* ── CSS Custom Properties (Design Tokens) ──────────────── */
:root {
    /* Light Theme (Converter) */
    --conv-bg: #f0f2f5;
    --conv-surface: #ffffff;
    --conv-text: #1a1a2e;
    --conv-text-secondary: #6b7280;
    --conv-accent: #6C63FF;
    --conv-accent-hover: #5A52D5;
    --conv-accent-light: rgba(108, 99, 255, 0.1);
    --conv-border: #e5e7eb;
    --conv-shadow: 0 4px 24px rgba(0, 0, 0, 0.06);
    --conv-shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.1);

    /* Dark Theme (Chat) */
    --chat-bg: #0a0a0f;
    --chat-surface: #12121a;
    --chat-surface-2: #1a1a2e;
    --chat-surface-3: #242442;
    --chat-text: #e8e8f0;
    --chat-text-secondary: #8888a8;
    --chat-accent: #00f5d4;
    --chat-accent-2: #7b2ff7;
    --chat-accent-3: #f72585;
    --chat-border: rgba(255, 255, 255, 0.06);
    --chat-glow: 0 0 20px rgba(0, 245, 212, 0.15);
    --chat-glow-strong: 0 0 40px rgba(0, 245, 212, 0.25);

    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    --font-xs: 0.7rem;
    --font-sm: 0.8rem;
    --font-base: 0.95rem;
    --font-md: 1.1rem;
    --font-lg: 1.35rem;
    --font-xl: 1.75rem;
    --font-2xl: 2.25rem;

    /* Spacing */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;

    /* Border Radius */
    --radius-sm: 6px;
    --radius-md: 12px;
    --radius-lg: 18px;
    --radius-xl: 24px;
    --radius-full: 9999px;

    /* Transitions */
    --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-in-out: cubic-bezier(0.65, 0, 0.35, 1);
    --duration-fast: 0.2s;
    --duration-normal: 0.35s;
    --duration-slow: 0.5s;

    /* Glassmorphism */
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(255, 255, 255, 0.3);
    --glass-blur: 16px;
    --glass-dark-bg: rgba(18, 18, 26, 0.8);
    --glass-dark-border: rgba(255, 255, 255, 0.08);
}

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

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

body {
    font-family: var(--font-family);
    line-height: 1.6;
    color: var(--conv-text);
    background: var(--conv-bg);
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

input, button, select, textarea {
    font-family: inherit;
    font-size: inherit;
    outline: none;
    border: none;
}

button {
    cursor: pointer;
    background: none;
}

a {
    text-decoration: none;
    color: inherit;
}

img, svg {
    display: block;
    max-width: 100%;
}

/* ── Layout ─────────────────────────────────────────────── */
#app {
    width: 100vw;
    height: 100vh;
    height: 100dvh;
    position: relative;
    overflow: hidden;
}

.layer {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    overflow-y: auto;
    overflow-x: hidden;
    transition: opacity var(--duration-slow) var(--ease-out),
                transform var(--duration-slow) var(--ease-out);
}

.layer.active {
    z-index: 10;
    opacity: 1;
    transform: scale(1);
    pointer-events: auto;
}

.layer.hidden {
    z-index: 1;
    opacity: 0;
    transform: scale(1.03);
    pointer-events: none;
    display: none;
}

/* Layer transition animations */
.layer.layer-enter {
    animation: layerEnter var(--duration-slow) var(--ease-out) forwards;
}

.layer.layer-exit {
    animation: layerExit var(--duration-slow) var(--ease-out) forwards;
}

@keyframes layerEnter {
    from {
        opacity: 0;
        transform: scale(0.96);
        filter: blur(4px);
    }
    to {
        opacity: 1;
        transform: scale(1);
        filter: blur(0);
    }
}

@keyframes layerExit {
    from {
        opacity: 1;
        transform: scale(1);
        filter: blur(0);
    }
    to {
        opacity: 0;
        transform: scale(1.04);
        filter: blur(4px);
    }
}

/* Chat layer always uses dark background */
#chat-layer {
    background: var(--chat-bg);
}

#converter-layer {
    background: var(--conv-bg);
}

/* ── Utility Classes ────────────────────────────────────── */
.hidden {
    display: none !important;
}

.glass {
    background: var(--glass-bg);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border: 1px solid var(--glass-border);
    border-radius: var(--radius-lg);
}

.glass-dark {
    background: var(--glass-dark-bg);
    backdrop-filter: blur(var(--glass-blur));
    -webkit-backdrop-filter: blur(var(--glass-blur));
    border: 1px solid var(--glass-dark-border);
    border-radius: var(--radius-lg);
}

/* ── Buttons ────────────────────────────────────────────── */
.btn-primary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 12px 28px;
    background: linear-gradient(135deg, var(--conv-accent), var(--conv-accent-hover));
    color: #fff;
    border: none;
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: var(--font-base);
    transition: all var(--duration-fast) var(--ease-out);
    box-shadow: 0 4px 16px rgba(108, 99, 255, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 24px rgba(108, 99, 255, 0.45);
}

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

.btn-secondary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 10px 24px;
    background: transparent;
    color: var(--conv-accent);
    border: 2px solid var(--conv-accent);
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: var(--font-base);
    transition: all var(--duration-fast) var(--ease-out);
}

.btn-secondary:hover {
    background: var(--conv-accent-light);
    transform: translateY(-1px);
}

.btn-ghost {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 8px 16px;
    background: transparent;
    color: var(--conv-text-secondary);
    border: none;
    border-radius: var(--radius-md);
    font-weight: 500;
    font-size: var(--font-sm);
    transition: all var(--duration-fast) var(--ease-out);
}

.btn-ghost:hover {
    background: rgba(0, 0, 0, 0.05);
    color: var(--conv-text);
}

/* Dark button variants */
.btn-primary-dark {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-sm);
    padding: 12px 28px;
    background: linear-gradient(135deg, var(--chat-accent), #00c4a7);
    color: #0a0a0f;
    border: none;
    border-radius: var(--radius-full);
    font-weight: 700;
    font-size: var(--font-base);
    transition: all var(--duration-fast) var(--ease-out);
    box-shadow: 0 4px 20px rgba(0, 245, 212, 0.25);
}

.btn-primary-dark:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 30px rgba(0, 245, 212, 0.4);
}

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

/* ── Inputs ─────────────────────────────────────────────── */
.input-field {
    width: 100%;
    padding: 12px 16px;
    background: var(--conv-surface);
    border: 2px solid var(--conv-border);
    border-radius: var(--radius-md);
    font-size: var(--font-base);
    color: var(--conv-text);
    transition: all var(--duration-fast) var(--ease-out);
}

.input-field:focus {
    border-color: var(--conv-accent);
    box-shadow: 0 0 0 4px var(--conv-accent-light);
}

.input-field::placeholder {
    color: var(--conv-text-secondary);
    opacity: 0.7;
}

.input-field-dark {
    width: 100%;
    padding: 12px 16px;
    background: var(--chat-surface);
    border: 2px solid var(--chat-border);
    border-radius: var(--radius-md);
    font-size: var(--font-base);
    color: var(--chat-text);
    transition: all var(--duration-fast) var(--ease-out);
}

.input-field-dark:focus {
    border-color: var(--chat-accent);
    box-shadow: 0 0 0 4px rgba(0, 245, 212, 0.1);
}

.input-field-dark::placeholder {
    color: var(--chat-text-secondary);
    opacity: 0.6;
}

/* ── Animations ─────────────────────────────────────────── */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes fadeOut {
    from { opacity: 1; }
    to { opacity: 0; }
}

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

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

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.5; }
}

@keyframes spin {
    from { transform: rotate(0deg); }
    to { transform: rotate(360deg); }
}

@keyframes glowPulse {
    0%, 100% { box-shadow: 0 0 5px rgba(0, 245, 212, 0.2); }
    50% { box-shadow: 0 0 20px rgba(0, 245, 212, 0.4); }
}

.fade-in { animation: fadeIn var(--duration-normal) var(--ease-out) forwards; }
.fade-out { animation: fadeOut var(--duration-normal) var(--ease-out) forwards; }
.slide-up { animation: slideUp var(--duration-normal) var(--ease-out) forwards; }
.slide-down { animation: slideDown var(--duration-normal) var(--ease-out) forwards; }

@keyframes scaleIn {
    from { opacity: 0.8; transform: scale(0.97); }
    to { opacity: 1; transform: scale(1); }
}

.scale-in { animation: scaleIn var(--duration-normal) var(--ease-out) forwards; }

.swap-btn.rotating {
    transform: rotate(180deg) scale(1.1);
    transition: transform 0.35s var(--ease-out);
}

/* ── Converter Styles ───────────────────────────────────── */
.converter-app {
    max-width: 580px;
    margin: 0 auto;
    padding: var(--space-lg);
    min-height: 100vh;
    min-height: 100dvh;
    display: flex;
    flex-direction: column;
}

.converter-header {
    text-align: center;
    padding: var(--space-2xl) 0 var(--space-lg);
    animation: slideDown var(--duration-slow) var(--ease-out);
}

.converter-header h1 {
    font-size: var(--font-2xl);
    font-weight: 800;
    background: linear-gradient(135deg, var(--conv-accent), var(--conv-accent-hover), #8b5cf6);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    letter-spacing: -0.03em;
}

.converter-header p {
    color: var(--conv-text-secondary);
    font-size: var(--font-sm);
    margin-top: var(--space-xs);
}

#converter-logo {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 56px;
    height: 56px;
    margin: 0 auto var(--space-md);
    background: linear-gradient(135deg, var(--conv-accent), #8b5cf6);
    border-radius: var(--radius-lg);
    font-size: 1.6rem;
    box-shadow: 0 4px 20px rgba(108, 99, 255, 0.3);
    cursor: default;
    user-select: none;
    -webkit-user-select: none;
    transition: transform var(--duration-fast) var(--ease-out);
}

#converter-logo:active {
    transform: scale(0.95);
}

.categories-container {
    display: flex;
    gap: var(--space-sm);
    overflow-x: auto;
    padding: var(--space-sm) 0 var(--space-md);
    scrollbar-width: none;
    -ms-overflow-style: none;
    animation: slideUp var(--duration-slow) var(--ease-out) 0.1s both;
}

.categories-container::-webkit-scrollbar {
    display: none;
}

.category-pill {
    flex-shrink: 0;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 18px;
    background: var(--conv-surface);
    border: 2px solid var(--conv-border);
    border-radius: var(--radius-full);
    font-size: var(--font-sm);
    font-weight: 500;
    color: var(--conv-text-secondary);
    cursor: pointer;
    transition: all var(--duration-fast) var(--ease-out);
    white-space: nowrap;
    user-select: none;
}

.category-pill:hover {
    border-color: var(--conv-accent);
    color: var(--conv-accent);
    background: var(--conv-accent-light);
}

.category-pill.active {
    background: var(--conv-accent);
    border-color: var(--conv-accent);
    color: #fff;
    box-shadow: 0 4px 16px rgba(108, 99, 255, 0.3);
}

.converter-card {
    background: var(--conv-surface);
    border-radius: var(--radius-xl);
    padding: var(--space-xl);
    box-shadow: var(--conv-shadow-lg);
    animation: slideUp var(--duration-slow) var(--ease-out) 0.2s both;
}

.converter-row {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.converter-unit-group {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.converter-unit-group label {
    font-size: var(--font-xs);
    font-weight: 600;
    color: var(--conv-text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

.converter-input {
    width: 100%;
    padding: 14px 16px;
    background: var(--conv-bg);
    border: 2px solid transparent;
    border-radius: var(--radius-md);
    font-size: var(--font-lg);
    font-weight: 600;
    color: var(--conv-text);
    transition: all var(--duration-fast) var(--ease-out);
}

.converter-input:focus {
    border-color: var(--conv-accent);
    background: var(--conv-surface);
    box-shadow: 0 0 0 4px var(--conv-accent-light);
}

.converter-input:read-only {
    color: var(--conv-accent);
    cursor: default;
}

.unit-select {
    width: 100%;
    padding: 10px 14px;
    background: var(--conv-bg);
    border: 2px solid transparent;
    border-radius: var(--radius-md);
    font-size: var(--font-base);
    font-weight: 500;
    color: var(--conv-text);
    cursor: pointer;
    transition: all var(--duration-fast) var(--ease-out);
    appearance: none;
    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 fill='%236b7280' d='M6 8.825L1.175 4 2.238 2.938 6 6.7 9.763 2.937 10.825 4z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 12px center;
    padding-right: 36px;
}

.unit-select:focus {
    border-color: var(--conv-accent);
}

.swap-btn-container {
    display: flex;
    justify-content: center;
    padding: var(--space-xs) 0;
}

.swap-btn {
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--conv-accent), var(--conv-accent-hover));
    color: #fff;
    display: flex;
    align-items: center;
    justify-content: center;
    border: none;
    cursor: pointer;
    transition: all var(--duration-fast) var(--ease-out);
    box-shadow: 0 4px 16px rgba(108, 99, 255, 0.3);
}

.swap-btn:hover {
    transform: rotate(180deg) scale(1.1);
    box-shadow: 0 6px 24px rgba(108, 99, 255, 0.4);
}

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

.converter-footer {
    margin-top: auto;
    text-align: center;
    padding: var(--space-xl) 0 var(--space-md);
    color: var(--conv-text-secondary);
    font-size: var(--font-xs);
    opacity: 0.7;
}

/* ── Chat Styles ────────────────────────────────────────── */
.chat-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
    height: 100dvh;
    max-width: 700px;
    margin: 0 auto;
    background: var(--chat-bg);
}

.chat-header {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md) var(--space-lg);
    background: var(--chat-surface);
    border-bottom: 1px solid var(--chat-border);
    z-index: 20;
}

.chat-header-title {
    font-size: var(--font-lg);
    font-weight: 700;
    color: var(--chat-accent);
    text-shadow: 0 0 30px rgba(0, 245, 212, 0.3);
    flex: 1;
}

.chat-header-icon {
    width: 32px;
    height: 32px;
    color: var(--chat-accent);
    opacity: 0.7;
}

.online-badge {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 4px 12px;
    background: rgba(0, 245, 212, 0.1);
    border-radius: var(--radius-full);
    font-size: var(--font-xs);
    color: var(--chat-accent);
    font-weight: 600;
}

.online-badge::before {
    content: '';
    width: 8px;
    height: 8px;
    background: var(--chat-accent);
    border-radius: 50%;
    animation: pulse 2s infinite;
}

.chat-header-btn {
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    color: var(--chat-text-secondary);
    transition: all var(--duration-fast) var(--ease-out);
}

.chat-header-btn:hover {
    background: var(--chat-surface-2);
    color: var(--chat-text);
}

.chat-header-btn.panic {
    color: var(--chat-accent-3);
}

.chat-header-btn.panic:hover {
    background: rgba(247, 37, 133, 0.15);
    color: var(--chat-accent-3);
}

/* Messages */
#messages-container {
    flex: 1;
    overflow-y: auto;
    padding: var(--space-md) var(--space-lg);
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
    scroll-behavior: smooth;
}

.msg-empty {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    flex: 1;
    color: var(--chat-text-secondary);
    font-size: var(--font-sm);
    gap: var(--space-md);
    opacity: 0.5;
}

.msg-empty svg {
    width: 48px;
    height: 48px;
    opacity: 0.3;
}

.msg-bubble {
    max-width: 75%;
    padding: 10px 14px;
    border-radius: var(--radius-lg);
    position: relative;
    animation: slideUp var(--duration-fast) var(--ease-out);
    overflow: hidden;
}

.msg-sent {
    align-self: flex-end;
    background: linear-gradient(135deg, var(--chat-accent-2), #5a1fd6);
    color: #fff;
    border-bottom-right-radius: var(--radius-sm);
}

.msg-received {
    align-self: flex-start;
    background: var(--chat-surface-2);
    color: var(--chat-text);
    border-bottom-left-radius: var(--radius-sm);
}

.msg-sender {
    font-size: var(--font-xs);
    font-weight: 600;
    color: var(--chat-accent);
    margin-bottom: 2px;
}

.msg-text {
    font-size: var(--font-base);
    line-height: 1.5;
    word-break: break-word;
}

.msg-time {
    font-size: 0.65rem;
    opacity: 0.6;
    text-align: right;
    margin-top: 4px;
}

.msg-expiring {
    animation: msgExpire 0.5s var(--ease-out) forwards;
}

@keyframes msgExpire {
    to {
        opacity: 0;
        transform: scale(0.95) translateY(-5px);
        max-height: 0;
        padding: 0;
        margin: 0;
    }
}

/* TTL Progress Bar */
.ttl-progress {
    position: absolute;
    bottom: 0;
    left: 0;
    height: 2px;
    background: linear-gradient(90deg, var(--chat-accent), var(--chat-accent-3));
    border-radius: 0 0 0 var(--radius-lg);
    transition: width 1s linear;
    opacity: 0.6;
}

/* Chat Input */
.chat-input-area {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-lg);
    background: var(--chat-surface);
    border-top: 1px solid var(--chat-border);
}

.ttl-btn {
    flex-shrink: 0;
    padding: 6px 12px;
    background: var(--chat-surface-2);
    border: 1px solid var(--chat-border);
    border-radius: var(--radius-full);
    font-size: var(--font-xs);
    font-weight: 700;
    color: var(--chat-accent);
    cursor: pointer;
    transition: all var(--duration-fast) var(--ease-out);
    white-space: nowrap;
}

.ttl-btn:hover {
    background: var(--chat-surface-3);
    box-shadow: var(--chat-glow);
}

.chat-input {
    flex: 1;
    padding: 10px 16px;
    background: var(--chat-surface-2);
    border: 1px solid var(--chat-border);
    border-radius: var(--radius-full);
    font-size: var(--font-base);
    color: var(--chat-text);
    transition: all var(--duration-fast) var(--ease-out);
}

.chat-input:focus {
    border-color: var(--chat-accent);
    box-shadow: 0 0 0 3px rgba(0, 245, 212, 0.1);
}

.chat-input::placeholder {
    color: var(--chat-text-secondary);
    opacity: 0.5;
}

.send-btn {
    flex-shrink: 0;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--chat-accent), #00c4a7);
    color: var(--chat-bg);
    display: flex;
    align-items: center;
    justify-content: center;
    border: none;
    cursor: pointer;
    transition: all var(--duration-fast) var(--ease-out);
    box-shadow: 0 4px 16px rgba(0, 245, 212, 0.25);
}

.send-btn:hover {
    transform: scale(1.08);
    box-shadow: 0 6px 24px rgba(0, 245, 212, 0.4);
}

.send-btn:active {
    transform: scale(0.95);
}

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

/* ── Auth Styles ────────────────────────────────────────── */
.auth-wrapper {
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    min-height: 100dvh;
    padding: var(--space-lg);
}

.auth-card {
    width: 100%;
    max-width: 420px;
    padding: var(--space-2xl) var(--space-xl);
    background: var(--chat-surface);
    border: 1px solid var(--chat-border);
    border-radius: var(--radius-xl);
    box-shadow: 0 0 60px rgba(0, 245, 212, 0.05);
    animation: slideUp var(--duration-slow) var(--ease-out);
}

.auth-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto var(--space-lg);
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, rgba(0, 245, 212, 0.1), rgba(123, 47, 247, 0.1));
    border-radius: var(--radius-lg);
    color: var(--chat-accent);
    animation: glowPulse 3s infinite;
}

.auth-icon svg {
    width: 32px;
    height: 32px;
}

.auth-title {
    text-align: center;
    font-size: var(--font-xl);
    font-weight: 700;
    color: var(--chat-text);
    margin-bottom: var(--space-xs);
}

.auth-subtitle {
    text-align: center;
    font-size: var(--font-sm);
    color: var(--chat-text-secondary);
    margin-bottom: var(--space-xl);
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: var(--space-md);
}

.auth-form .input-field-dark {
    padding: 14px 16px;
}

.auth-error {
    padding: 10px 14px;
    background: rgba(247, 37, 133, 0.1);
    border: 1px solid rgba(247, 37, 133, 0.2);
    border-radius: var(--radius-md);
    color: var(--chat-accent-3);
    font-size: var(--font-sm);
    text-align: center;
    animation: slideUp var(--duration-fast) var(--ease-out);
}

.auth-toggle {
    text-align: center;
    margin-top: var(--space-lg);
    font-size: var(--font-sm);
    color: var(--chat-text-secondary);
}

.auth-toggle a {
    color: var(--chat-accent);
    font-weight: 600;
    cursor: pointer;
    transition: opacity var(--duration-fast);
}

.auth-toggle a:hover {
    opacity: 0.8;
}

.auth-spinner {
    width: 20px;
    height: 20px;
    border: 2px solid transparent;
    border-top-color: currentColor;
    border-radius: 50%;
    animation: spin 0.6s linear infinite;
    display: inline-block;
}

/* ── Dark Scrollbar ─────────────────────────────────────── */
#chat-layer ::-webkit-scrollbar {
    width: 6px;
}

#chat-layer ::-webkit-scrollbar-track {
    background: transparent;
}

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

#chat-layer ::-webkit-scrollbar-thumb:hover {
    background: var(--chat-text-secondary);
}

/* ── Responsive ─────────────────────────────────────────── */
@media (max-width: 600px) {
    :root {
        --font-2xl: 1.75rem;
        --font-xl: 1.4rem;
        --font-lg: 1.15rem;
    }

    .converter-app {
        padding: var(--space-md);
    }

    .converter-card {
        padding: var(--space-lg);
    }

    .converter-header {
        padding: var(--space-xl) 0 var(--space-md);
    }

    .chat-header {
        padding: var(--space-sm) var(--space-md);
    }

    .chat-input-area {
        padding: var(--space-sm) var(--space-md);
    }

    #messages-container {
        padding: var(--space-sm) var(--space-md);
    }

    .msg-bubble {
        max-width: 85%;
    }

    .auth-card {
        padding: var(--space-xl) var(--space-lg);
    }
}