/* ============================================================
   QR Code Generator — Material Design 3 Expressive
   Teal / Light-Blue palette · Light + Dark themes
   Advanced layout: fixed header, scrollable controls, sticky preview
   ============================================================ */

/* ---------- Google Fonts ---------- */
@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600&family=Outfit:wght@500;600;700&display=swap');

/* ================================================================
   MD3 Color Tokens — DARK (default)
   ================================================================ */
:root {
    /* Primary — Teal */
    --md-primary: #80cbc4;
    --md-on-primary: #003731;
    --md-primary-container: #004d47;
    --md-on-primary-container: #a7f3ec;

    /* Secondary */
    --md-secondary: #b0ccc8;
    --md-on-secondary: #1b3531;
    --md-secondary-container: #324b47;
    --md-on-secondary-container: #cce8e3;

    /* Tertiary — Light Blue accent */
    --md-tertiary: #81d4fa;
    --md-on-tertiary: #003549;
    --md-tertiary-container: #004d6a;
    --md-on-tertiary-container: #b8eaff;

    /* Surface / Background */
    --md-surface: #0f1513;
    --md-surface-dim: #0f1513;
    --md-surface-bright: #353b39;
    --md-surface-container-lowest: #0a100e;
    --md-surface-container-low: #171d1b;
    --md-surface-container: #1b2120;
    --md-surface-container-high: #262c2a;
    --md-surface-container-highest: #313735;
    --md-on-surface: #e0e3e1;
    --md-on-surface-variant: #bec9c5;
    --md-outline: #889390;
    --md-outline-variant: #3f4946;

    /* Error */
    --md-error: #ffb4ab;
    --md-on-error: #690005;

    /* Misc */
    --md-shadow: rgba(0, 0, 0, .35);

    /* Shape */
    --shape-xl: 28px;
    --shape-lg: 16px;
    --shape-md: 12px;
    --shape-sm: 8px;

    /* Elevation */
    --elevation-1: 0 1px 3px 1px var(--md-shadow), 0 1px 2px 0 var(--md-shadow);
    --elevation-2: 0 2px 6px 2px var(--md-shadow), 0 1px 2px 0 var(--md-shadow);
    --elevation-3: 0 4px 8px 3px var(--md-shadow), 0 1px 3px 0 var(--md-shadow);

    /* Gradient accent */
    --gradient-accent: linear-gradient(135deg, #80cbc4 0%, #81d4fa 100%);

    /* Focus ring */
    --focus-ring: rgba(128, 203, 196, .22);

    /* Glassmorphism bg */
    --glass-bg: rgba(27, 33, 32, .65);

    /* Header height token */
    --header-height: 80px;

    color-scheme: dark;
}

/* ================================================================
   MD3 Color Tokens — LIGHT
   ================================================================ */
[data-theme="light"] {
    --md-primary: #006b63;
    --md-on-primary: #ffffff;
    --md-primary-container: #a7f3ec;
    --md-on-primary-container: #00201d;

    --md-secondary: #4a6560;
    --md-on-secondary: #ffffff;
    --md-secondary-container: #cce8e3;
    --md-on-secondary-container: #06201c;

    --md-tertiary: #0277bd;
    --md-on-tertiary: #ffffff;
    --md-tertiary-container: #b8eaff;
    --md-on-tertiary-container: #001f2d;

    --md-surface: #f5faf8;
    --md-surface-dim: #d5dbd9;
    --md-surface-bright: #f5faf8;
    --md-surface-container-lowest: #ffffff;
    --md-surface-container-low: #eff5f3;
    --md-surface-container: #e9efed;
    --md-surface-container-high: #e4eae8;
    --md-surface-container-highest: #dee4e2;
    --md-on-surface: #171d1b;
    --md-on-surface-variant: #3f4946;
    --md-outline: #6f7976;
    --md-outline-variant: #bec9c5;

    --md-error: #ba1a1a;
    --md-on-error: #ffffff;

    --md-shadow: rgba(0, 0, 0, .12);
    --gradient-accent: linear-gradient(135deg, #006b63 0%, #0277bd 100%);
    --focus-ring: rgba(0, 107, 99, .18);
    --glass-bg: rgba(233, 239, 237, .75);

    color-scheme: light;
}

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

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', system-ui, sans-serif;
    background: var(--md-surface);
    color: var(--md-on-surface);
    min-height: 100vh;
    line-height: 1.55;
    -webkit-font-smoothing: antialiased;
    transition: background .35s ease, color .35s ease;
    overflow: hidden;
    /* desktop: no body scroll */
}

/* ---------- Typography ---------- */
h1,
h2,
h3,
h4 {
    font-family: 'Outfit', sans-serif;
    font-weight: 600;
    letter-spacing: -0.01em;
}

/* =================================================================
   App Shell — Fixed header + split body
   ================================================================= */

.app-shell {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

/* ---- Header (fixed) ---- */
.app-header {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: .85rem 1.5rem;
    position: relative;
    flex-shrink: 0;
    z-index: 10;
    background: var(--md-surface);
    border-bottom: 1px solid var(--md-outline-variant);
    transition: background .35s ease, border-color .35s ease;
}

.app-header-center {
    text-align: center;
}

.app-header h1 {
    font-size: 1.65rem;
    font-weight: 700;
    background: var(--gradient-accent);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.app-header p {
    color: var(--md-on-surface-variant);
    font-size: .82rem;
    margin-top: .15rem;
}

/* Theme toggle */
.theme-toggle {
    position: absolute;
    right: 1.5rem;
    top: 50%;
    transform: translateY(-50%);
    display: flex;
    align-items: center;
    gap: .55rem;
}

.theme-toggle .toggle-label {
    font-size: .78rem;
    color: var(--md-on-surface-variant);
    user-select: none;
}

/* ---- Main Layout (fills remaining height) ---- */
.app-layout {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1.25rem;
    flex: 1;
    min-height: 0;
    /* let children shrink */
    padding: 1.25rem 1.5rem;
    max-width: 1280px;
    margin: 0 auto;
    width: 100%;
}

/* ---------- Panels ---------- */
.panel {
    background: var(--md-surface-container);
    border-radius: var(--shape-xl);
    padding: 1.5rem;
    box-shadow: var(--elevation-2);
    overflow: hidden;
    /* clip children to border-radius */
    transition: background .35s ease, box-shadow .35s ease;
}

/* Controls: stealth-scrollable (hidden scrollbar, full scroll) */
.controls-panel {
    overflow-y: auto;
    overflow-x: hidden;
    /* kill Firefox horizontal scrollbar */
    min-height: 0;
    /* Stealth scrollbar — Firefox/Gecko */
    scrollbar-width: none;
    /* Bottom fade hint: subtle cue that content continues */
    -webkit-mask-image: linear-gradient(to bottom,
            black 0%,
            black calc(100% - 36px),
            transparent 100%);
    mask-image: linear-gradient(to bottom,
            black 0%,
            black calc(100% - 36px),
            transparent 100%);
}

/* Stealth scrollbar — Chrome/Blink/WebKit */
.controls-panel::-webkit-scrollbar {
    display: none;
}

/* Generic panel title — flush, no background, not sticky */
.panel-title {
    font-size: 1.05rem;
    margin-bottom: 1.15rem;
    color: var(--md-primary);
    display: flex;
    align-items: center;
    gap: .5rem;
    position: relative;
    /* scrolls with content */
}

.panel-title .icon {
    font-size: 1.15rem;
}

/* Controls-only: sticky header with opaque mask */
.controls-panel>.panel-title {
    position: sticky;
    top: -1.5rem;
    z-index: 3;
    background: var(--md-surface-container);
    padding: .55rem 0;
    /* Full-width bleed: negate parent padding so divider spans edge-to-edge */
    margin: -1.5rem -1.5rem 1.15rem;
    padding-left: 1.5rem;
    padding-right: 1.5rem;
    width: calc(100% + 3rem);
    border-bottom: 1px solid var(--md-outline-variant);
    border-radius: var(--shape-xl) var(--shape-xl) 0 0;
    transition: background .35s ease, border-color .35s ease;
}

/* ---------- Preview Panel (Glassmorphism / fixed in view) ---------- */
.preview-panel {
    display: flex;
    flex-direction: column;
    align-items: center;
    overflow-y: auto;
    overflow-x: hidden;
    min-height: 0;
    background: var(--glass-bg);
    backdrop-filter: blur(24px) saturate(1.4);
    -webkit-backdrop-filter: blur(24px) saturate(1.4);
    border: 1px solid var(--md-outline-variant);
    transition: background .35s ease, border-color .35s ease;
    /* Stealth scrollbar */
    scrollbar-width: none;
}

.preview-panel::-webkit-scrollbar {
    display: none;
}

/* Preview title: not sticky, scrolls naturally */
.preview-panel>.panel-title {
    position: relative;
    background: transparent;
    width: 100%;
    justify-content: center;
}

.qr-preview-wrapper {
    width: 100%;
    max-width: 320px;
    aspect-ratio: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--md-surface-container-lowest);
    border-radius: var(--shape-lg);
    overflow: hidden;
    margin-bottom: 1.25rem;
    position: relative;
    flex-shrink: 0;
    transition: background .35s ease;
}

/* Checkerboard for transparent backgrounds */
.qr-preview-wrapper::before {
    content: '';
    position: absolute;
    inset: 0;
    background-image:
        linear-gradient(45deg, #ccc 25%, transparent 25%),
        linear-gradient(-45deg, #ccc 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, #ccc 75%),
        linear-gradient(-45deg, transparent 75%, #ccc 75%);
    background-size: 16px 16px;
    background-position: 0 0, 0 8px, 8px -8px, -8px 0;
    opacity: .2;
    border-radius: inherit;
}

.qr-preview-wrapper canvas,
.qr-preview-wrapper svg {
    position: relative;
    z-index: 1;
    max-width: 100%;
    max-height: 100%;
}

/* ---------- Sections ---------- */
.control-section {
    background: var(--md-surface-container-high);
    border-radius: var(--shape-lg);
    padding: 1.15rem;
    margin-bottom: .85rem;
    transition: box-shadow .2s ease, background .35s ease;
}

.control-section:hover {
    box-shadow: var(--elevation-1);
}

.section-header {
    font-family: 'Outfit', sans-serif;
    font-size: .92rem;
    font-weight: 600;
    color: var(--md-on-surface);
    margin-bottom: .85rem;
    display: flex;
    align-items: center;
    gap: .45rem;
}

.section-header .icon {
    color: var(--md-tertiary);
}

/* ---------- Form Controls ---------- */
.field-group {
    margin-bottom: .85rem;
}

.field-group:last-child {
    margin-bottom: 0;
}

label {
    display: block;
    font-size: .78rem;
    font-weight: 500;
    color: var(--md-on-surface-variant);
    margin-bottom: .35rem;
    letter-spacing: .02em;
}

/* Text Input */
input[type="text"],
input[type="url"],
input[type="number"],
textarea {
    width: 100%;
    padding: .75rem .9rem;
    font-family: 'Inter', sans-serif;
    font-size: .9rem;
    color: var(--md-on-surface);
    background: var(--md-surface-container-lowest);
    border: 1.5px solid var(--md-outline-variant);
    border-radius: var(--shape-md);
    outline: none;
    transition: border-color .2s, box-shadow .2s, background .35s ease, color .35s ease;
}

input[type="text"]:focus,
input[type="url"]:focus,
input[type="number"]:focus,
textarea:focus {
    border-color: var(--md-primary);
    box-shadow: 0 0 0 3px var(--focus-ring);
}

/* Select */
select {
    width: 100%;
    padding: .65rem .8rem;
    font-family: 'Inter', sans-serif;
    font-size: .85rem;
    color: var(--md-on-surface);
    background: var(--md-surface-container-lowest);
    border: 1.5px solid var(--md-outline-variant);
    border-radius: var(--shape-md);
    outline: none;
    cursor: pointer;
    appearance: none;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='12' height='7'%3E%3Cpath d='M1 1l5 5 5-5' stroke='%23889390' stroke-width='1.5' fill='none'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right .85rem center;
    transition: border-color .2s ease, background .35s ease, color .35s ease;
}

select:focus {
    border-color: var(--md-primary);
}

/* Color Picker */
.color-input-group {
    display: flex;
    align-items: center;
    gap: .6rem;
}

input[type="color"] {
    -webkit-appearance: none;
    appearance: none;
    width: 38px;
    height: 38px;
    border: 2px solid var(--md-outline-variant);
    border-radius: var(--shape-sm);
    cursor: pointer;
    background: none;
    padding: 2px;
    flex-shrink: 0;
    transition: border-color .2s;
}

input[type="color"]:hover {
    border-color: var(--md-primary);
}

input[type="color"]::-webkit-color-swatch-wrapper {
    padding: 0;
}

input[type="color"]::-webkit-color-swatch {
    border: none;
    border-radius: 4px;
}

.color-hex {
    font-family: 'Inter', monospace;
    font-size: .8rem;
    color: var(--md-on-surface-variant);
    min-width: 58px;
}

/* Range / Slider */
input[type="range"] {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 5px;
    background: var(--md-outline-variant);
    border-radius: 3px;
    outline: none;
    cursor: pointer;
}

input[type="range"]::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    background: var(--md-primary);
    border-radius: 50%;
    border: 3px solid var(--md-surface-container);
    box-shadow: var(--elevation-1);
    transition: transform .15s ease;
}

input[type="range"]::-webkit-slider-thumb:hover {
    transform: scale(1.15);
}

input[type="range"]::-moz-range-thumb {
    width: 18px;
    height: 18px;
    background: var(--md-primary);
    border-radius: 50%;
    border: 3px solid var(--md-surface-container);
    box-shadow: var(--elevation-1);
}

/* Toggle (checkbox as switch) */
.toggle-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: .75rem;
}

.toggle-label {
    font-size: .83rem;
    color: var(--md-on-surface);
}

.switch {
    position: relative;
    width: 48px;
    height: 28px;
    flex-shrink: 0;
}

.switch input {
    opacity: 0;
    width: 0;
    height: 0;
}

.switch .slider {
    position: absolute;
    inset: 0;
    background: var(--md-outline-variant);
    border-radius: 14px;
    cursor: pointer;
    transition: background .25s ease;
}

.switch .slider::before {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    left: 4px;
    top: 4px;
    background: var(--md-on-surface);
    border-radius: 50%;
    transition: transform .25s ease, background .25s ease;
}

.switch input:checked+.slider {
    background: var(--md-primary);
}

.switch input:checked+.slider::before {
    transform: translateX(20px);
    background: var(--md-on-primary);
}

/* ---------- Segmented Button ---------- */
.segmented-group {
    display: flex;
    border: 1.5px solid var(--md-outline-variant);
    border-radius: var(--shape-md);
    overflow: hidden;
}

.segmented-group input[type="radio"] {
    display: none;
}

.segmented-group label {
    flex: 1;
    text-align: center;
    padding: .55rem .4rem;
    font-size: .78rem;
    font-weight: 500;
    color: var(--md-on-surface-variant);
    cursor: pointer;
    border-right: 1px solid var(--md-outline-variant);
    transition: background .2s, color .2s;
    margin-bottom: 0;
}

.segmented-group label:last-of-type {
    border-right: none;
}

.segmented-group input[type="radio"]:checked+label {
    background: var(--md-primary-container);
    color: var(--md-on-primary-container);
}

/* ---------- Buttons ---------- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: .45rem;
    padding: .65rem 1.25rem;
    font-family: 'Inter', sans-serif;
    font-size: .82rem;
    font-weight: 600;
    border: none;
    border-radius: var(--shape-md);
    cursor: pointer;
    transition: transform .15s ease, box-shadow .2s ease, opacity .2s ease, background .35s ease, color .35s ease;
    white-space: nowrap;
}

.btn:hover {
    transform: translateY(-1px);
    box-shadow: var(--elevation-2);
}

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

.btn-filled {
    background: var(--gradient-accent);
    color: var(--md-on-primary);
}

.btn-tonal {
    background: var(--md-secondary-container);
    color: var(--md-on-secondary-container);
}

.btn-outlined {
    background: transparent;
    color: var(--md-primary);
    border: 1.5px solid var(--md-outline);
}

.btn-outlined:hover {
    background: var(--focus-ring);
}

/* Icon button (small) */
.btn-icon {
    width: 36px;
    height: 36px;
    padding: 0;
    border-radius: 50%;
    font-size: 1.1rem;
    background: var(--md-surface-container-high);
    color: var(--md-on-surface-variant);
    border: 1px solid var(--md-outline-variant);
    display: inline-flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: background .2s, color .2s, transform .15s;
    flex-shrink: 0;
}

.btn-icon:hover {
    background: var(--md-primary-container);
    color: var(--md-on-primary-container);
    transform: scale(1.08);
}

/* Button groups */
.btn-row {
    display: flex;
    flex-wrap: wrap;
    gap: .55rem;
}

.btn-row .btn {
    flex: 1;
    min-width: 0;
}

/* ---------- File Upload Area ---------- */
.upload-area {
    border: 2px dashed var(--md-outline-variant);
    border-radius: var(--shape-md);
    padding: 1.25rem .85rem;
    text-align: center;
    cursor: pointer;
    transition: border-color .2s, background .2s;
    position: relative;
}

.upload-area:hover {
    border-color: var(--md-primary);
    background: var(--focus-ring);
}

.upload-area input[type="file"] {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}

.upload-area .upload-icon {
    font-size: 1.75rem;
    margin-bottom: .25rem;
}

.upload-area .upload-text {
    font-size: .78rem;
    color: var(--md-on-surface-variant);
}

.logo-preview-container {
    display: flex;
    align-items: center;
    gap: .65rem;
    margin-top: .65rem;
}

.logo-preview-container img {
    width: 44px;
    height: 44px;
    border-radius: var(--shape-sm);
    object-fit: contain;
    background: var(--md-surface-container-lowest);
    border: 1px solid var(--md-outline-variant);
}

.logo-preview-container .remove-logo {
    font-size: .75rem;
    color: var(--md-error);
    cursor: pointer;
    background: none;
    border: none;
    font-weight: 600;
}

/* ---------- Gradient Sub-controls ---------- */
.gradient-controls {
    display: none;
    flex-direction: column;
    gap: .75rem;
    margin-top: .75rem;
    padding-top: .75rem;
    border-top: 1px solid var(--md-outline-variant);
}

.gradient-controls.visible {
    display: flex;
}

.gradient-row {
    display: flex;
    align-items: center;
    gap: .65rem;
}

/* ---------- Export Section ---------- */
.export-section {
    margin-top: 1rem;
    width: 100%;
}

.export-section .section-header {
    margin-bottom: .65rem;
}

.export-header-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: .65rem;
}

.export-header-row .section-header {
    margin-bottom: 0;
}

/* Resolution picker */
.resolution-picker {
    display: none;
    margin-bottom: .65rem;
}

.resolution-picker.visible {
    display: block;
}

/* ---------- Template / Gallery Section ---------- */
.template-section {
    margin-top: .65rem;
    padding-top: .85rem;
    border-top: 1px solid var(--md-outline-variant);
    width: 100%;
}

/* Session Gallery Grid */
.session-gallery {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: .55rem;
    margin-top: .65rem;
    max-height: 240px;
    overflow-y: auto;
    scrollbar-width: thin;
    scrollbar-color: var(--md-outline-variant) transparent;
}

.session-gallery::-webkit-scrollbar {
    width: 4px;
}

.session-gallery::-webkit-scrollbar-thumb {
    background: var(--md-outline-variant);
    border-radius: 2px;
}

.gallery-card {
    position: relative;
    border-radius: var(--shape-sm);
    overflow: hidden;
    border: 2px solid var(--md-outline-variant);
    cursor: pointer;
    transition: border-color .2s, transform .15s;
    aspect-ratio: 1;
    background: var(--md-surface-container-lowest);
}

.gallery-card:hover {
    border-color: var(--md-primary);
    transform: scale(1.04);
}

.gallery-card img {
    width: 100%;
    height: 100%;
    object-fit: contain;
    display: block;
}

.gallery-card .gallery-delete {
    position: absolute;
    top: 3px;
    right: 3px;
    width: 20px;
    height: 20px;
    border-radius: 50%;
    background: var(--md-error);
    color: var(--md-on-error);
    border: none;
    font-size: .65rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity .2s;
    z-index: 2;
    line-height: 1;
}

.gallery-card:hover .gallery-delete {
    opacity: 1;
}

.gallery-empty {
    grid-column: 1 / -1;
    text-align: center;
    color: var(--md-on-surface-variant);
    font-size: .78rem;
    padding: 1rem;
    font-style: italic;
}

.gallery-limit-note {
    font-size: .7rem;
    color: var(--md-on-surface-variant);
    margin-top: .35rem;
    text-align: center;
}

/* ---------- Toast ---------- */
.toast {
    position: fixed;
    bottom: 1.5rem;
    left: 50%;
    transform: translateX(-50%) translateY(120px);
    background: var(--md-surface-container-highest);
    color: var(--md-on-surface);
    padding: .75rem 1.35rem;
    border-radius: var(--shape-md);
    box-shadow: var(--elevation-3);
    font-size: .85rem;
    z-index: 1000;
    opacity: 0;
    transition: transform .35s cubic-bezier(.4, 0, .2, 1), opacity .35s ease;
    pointer-events: none;
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

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

/* ---------- Responsive ---------- */
@media (max-width: 900px) {
    body {
        overflow: auto;
    }

    .app-shell {
        height: auto;
        min-height: 100vh;
    }

    .app-layout {
        grid-template-columns: 1fr;
        height: auto;
    }

    .preview-panel {
        order: -1;
        max-height: none;
        overflow-y: visible;
    }

    .controls-panel {
        overflow-y: visible;
    }

    .qr-preview-wrapper {
        max-width: 260px;
    }

    .theme-toggle {
        position: static;
        transform: none;
        margin-top: .35rem;
    }

    .app-header {
        flex-direction: column;
    }

    .session-gallery {
        grid-template-columns: repeat(4, 1fr);
    }
}

@media (max-width: 480px) {
    .app-header h1 {
        font-size: 1.35rem;
    }

    .panel {
        padding: 1.15rem;
        border-radius: 20px;
    }

    .btn-row .btn {
        font-size: .78rem;
        padding: .55rem .85rem;
    }

    .session-gallery {
        grid-template-columns: repeat(3, 1fr);
    }
}