:root {
    --bg-color: #f6f5fa;
    --surface: #ffffff;
    --text-primary: #1f1d2b;
    --text-secondary: #5f5b72;
    --border: #e3e0ee;
    --border-strong: #c9c3dc;
    --accent: #7c3aed;
    --accent-hover: #6d28d9;
    --accent-soft: #f1eafe;
    --danger-bg: #fef2f2;
    --danger-border: #fecaca;
    --danger-text: #b91c1c;
    --pattern: #d4d0e2;
    --radius: 1rem;
    --shadow: 0 1px 2px rgba(31, 29, 43, 0.05), 0 4px 16px rgba(31, 29, 43, 0.06);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.5;
}

/* Container */
.container {
    width: 100%;
    max-width: 960px;
    margin: 0 auto;
    padding: 2.5rem 1rem 4rem;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Header */
header {
    text-align: center;
}

.logo {
    font-size: 2.75rem;
    font-weight: 800;
    letter-spacing: -1px;
}

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

.subtitle,
.muted {
    color: var(--text-secondary);
}

.small {
    font-size: 0.85rem;
}

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

.panel {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
}

.panel-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 1rem;
    flex-wrap: wrap;
    margin-bottom: 1rem;
}

.panel h2 {
    font-size: 1.25rem;
}

/* Drop Zone */
.drop-zone {
    background: var(--surface);
    border: 2px dashed var(--border-strong);
    border-radius: var(--radius);
    padding: 2.5rem 1.5rem;
    text-align: center;
    cursor: pointer;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.5rem;
    color: var(--text-secondary);
    transition: border-color 0.2s ease, background-color 0.2s ease;
}

.drop-zone svg {
    color: var(--accent);
}

.drop-zone h2 {
    color: var(--text-primary);
    font-size: 1.25rem;
}

.drop-zone:hover,
.drop-zone.dragover {
    border-color: var(--accent);
    background: var(--accent-soft);
}

.drop-zone:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 4px;
}

.file-hint {
    font-size: 0.85rem;
}

/* Templates */
.templates {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    margin-top: 1rem;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.chip {
    background: var(--surface);
    border: 1px solid var(--border-strong);
    color: var(--text-primary);
    padding: 0.4rem 0.9rem;
    font-size: 0.85rem;
    font-weight: 500;
}

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

/* Feedback */
.error-message {
    margin-top: 1rem;
    padding: 0.875rem 1.25rem;
    border-radius: var(--radius);
    background: var(--danger-bg);
    border: 1px solid var(--danger-border);
    color: var(--danger-text);
    font-size: 0.95rem;
    white-space: pre-line;
}

.status-text {
    margin-top: 0.75rem;
    text-align: center;
    color: var(--text-secondary);
    font-size: 0.9rem;
    min-height: 1.35em;
}

/* Buttons */
button {
    font: inherit;
    font-weight: 600;
    font-size: 0.95rem;
    padding: 0.6rem 1.25rem;
    border-radius: 999px;
    cursor: pointer;
    border: none;
    transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
}

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

button:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}

.primary-btn {
    background: var(--accent);
    color: #ffffff;
}

.primary-btn:hover:not(:disabled) {
    background: var(--accent-hover);
}

.secondary-btn {
    background: var(--accent-soft);
    color: var(--accent);
}

.secondary-btn:hover {
    background: #e6dafd;
}

.ghost-btn {
    background: transparent;
    color: var(--text-secondary);
}

.ghost-btn:hover {
    color: var(--danger-text);
}

.toolbar {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

/* Page grid */
.page-grid {
    list-style: none;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 0.75rem;
    margin: 0.75rem 0 1.5rem;
}

.page-card {
    background: var(--bg-color);
    border: 1px solid var(--border);
    border-radius: 0.75rem;
    padding: 0.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
    cursor: grab;
}

.page-card.dragging {
    opacity: 0.4;
}

.page-card.drop-target {
    border-color: var(--accent);
    box-shadow: 0 0 0 2px var(--accent-soft);
}

.thumb {
    aspect-ratio: 210 / 297;
    background: #ffffff;
    border: 1px solid var(--border);
    border-radius: 0.25rem;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
}

.thumb img {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
    pointer-events: none;
}

.thumb.filler-lined {
    background-image: repeating-linear-gradient(to bottom, transparent 0 9px, var(--pattern) 9px 10px);
}

.thumb.filler-grid {
    background-image:
        repeating-linear-gradient(to bottom, transparent 0 6px, var(--pattern) 6px 7px),
        repeating-linear-gradient(to right, transparent 0 6px, var(--pattern) 6px 7px);
}

.thumb.filler-dots {
    background-image: radial-gradient(var(--pattern) 1px, transparent 1.2px);
    background-size: 7px 7px;
}

.card-meta {
    display: flex;
    flex-direction: column;
    font-size: 0.75rem;
    min-width: 0;
}

.card-label {
    color: var(--text-secondary);
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.card-actions {
    display: flex;
    justify-content: space-between;
}

.icon-btn {
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text-primary);
    padding: 0.15rem 0.6rem;
    font-size: 0.9rem;
    line-height: 1.4;
}

.icon-btn:hover:not(:disabled) {
    border-color: var(--accent);
    color: var(--accent);
}

/* Options */
.options {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem 2rem;
}

fieldset {
    border: none;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem 1rem;
}

legend {
    font-weight: 600;
    margin-bottom: 0.4rem;
    width: 100%;
}

fieldset label {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    cursor: pointer;
    color: var(--text-secondary);
}

input[type="radio"] {
    accent-color: var(--accent);
}

/* Preview */
.preview {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    min-height: 120px;
    transition: opacity 0.2s ease;
}

.preview.loading {
    opacity: 0.4;
}

.sheet-canvas {
    width: 100%;
    height: auto;
    border: 1px solid var(--border);
    border-radius: 0.25rem;
    background: #ffffff;
}

/* Folding Guide */
.folding-guide summary {
    font-weight: 700;
    font-size: 1.1rem;
    cursor: pointer;
}

.steps {
    margin-top: 1rem;
    padding-left: 1.5rem;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    color: var(--text-secondary);
}

/* Responsive */
@media (max-width: 600px) {
    .logo {
        font-size: 2rem;
    }

    .panel {
        padding: 1rem;
    }

    .panel-header > button,
    .toolbar {
        width: 100%;
    }

    .toolbar button {
        flex: 1 1 auto;
        white-space: nowrap;
        padding: 0.6rem 0.9rem;
    }
}

@media (prefers-reduced-motion: reduce) {
    .drop-zone, button, .preview {
        transition: none;
    }
}