:root {
    /* Farbschema */
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-color: #f8fafc;
    --surface-color: #ffffff;
    --text-main: #0f172a;
    --text-muted: #64748b;
    --border-color: #e2e8f0;
    
    /* Layout & Design */
    --radius: 8px;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --transition: 0.2s ease-in-out;
}

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

body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.5;
}

.container {
    max-width: 1200px;
    margin-inline: auto;
    padding-inline: 1.5rem;
}

/* Header */
.app-header {
    background-color: var(--surface-color);
    border-block-end: 1px solid var(--border-color);
    padding-block: 1rem;
    margin-block-end: 2rem;
}

.header-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.lang-selector select {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    background-color: var(--surface-color);
    cursor: pointer;
}

/* Main Layout (Grid) */
.app-main {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
    align-items: start;
    margin-block-end: 4rem;
}

@media (min-width: 768px) {
    .app-main {
        grid-template-columns: 2fr 1fr;
    }
}

/* Linke Spalte: Konfiguration */
.config-panel {
    background-color: var(--surface-color);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
}

/* Tabs */
.tabs {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    border-block-end: 2px solid var(--border-color);
    margin-block-end: 1.5rem;
}

.tabs button {
    background: none;
    border: none;
    padding: 0.75rem 1.25rem;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text-muted);
    cursor: pointer;
    border-block-end: 2px solid transparent;
    margin-block-end: -2px; /* Überlappt den Container-Border */
    transition: var(--transition);
}

.tabs button:hover {
    color: var(--primary-color);
}

.tabs button[aria-selected="true"] {
    color: var(--primary-color);
    border-block-end-color: var(--primary-color);
}

/* Tab Content */
.tab-content {
    display: none;
    animation: fadeIn 0.3s ease;
}

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

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(5px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Formulare */
.form-group {
    margin-block-end: 1rem;
    display: flex;
    flex-direction: column;
}

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

@media (min-width: 600px) {
    .form-row {
        grid-template-columns: 1fr 1fr;
    }
}

label {
    font-weight: 500;
    margin-block-end: 0.5rem;
    font-size: 0.9rem;
}

input[type="text"],
input[type="url"],
input[type="email"],
input[type="tel"],
textarea,
select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    font-family: inherit;
    transition: var(--transition);
}

input:focus, textarea:focus, select:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.checkbox-group {
    flex-direction: row;
    align-items: center;
    gap: 0.5rem;
    margin-top: 1.8rem; /* Alignment mit Select-Boxen */
}

/* Accordions */
.accordion {
    margin-block-start: 1.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    overflow: hidden;
}

.accordion summary {
    padding: 1rem;
    font-weight: 600;
    background-color: #f1f5f9;
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.accordion summary::-webkit-details-marker {
    display: none;
}

.accordion summary::after {
    content: "▼";
    font-size: 0.8rem;
    transition: transform var(--transition);
}

.accordion[open] summary::after {
    transform: rotate(180deg);
}

.accordion-content {
    padding: 1rem;
    border-block-start: 1px solid var(--border-color);
}

input[type="color"] {
    width: 100%;
    height: 40px;
    padding: 0;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    cursor: pointer;
}

/* Rechte Spalte: Vorschau */
.preview-panel {
    background-color: var(--surface-color);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.5rem;
    position: sticky;
    top: 2rem;
    text-align: center;
}

.preview-panel h2 {
    font-size: 1.25rem;
    margin-block-end: 1.5rem;
}

.qr-preview-wrapper {
    position: relative;
    width: 100%;
    max-width: 300px;
    aspect-ratio: 1 / 1;
    margin-inline: auto;
    margin-block-end: 1.5rem;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    padding: 1rem;
    background-color: #fff;
}

#qr-preview {
    width: 100%;
    height: 100%;
    object-fit: contain;
    transition: opacity var(--transition);
}

/* Spinner */
.spinner {
    position: absolute;
    inset: 0;
    background: rgba(255, 255, 255, 0.8);
    display: flex;
    justify-content: center;
    align-items: center;
}

.spinner::after {
    content: "";
    width: 40px;
    height: 40px;
    border: 4px solid var(--border-color);
    border-block-start-color: var(--primary-color);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

.spinner.hidden {
    display: none;
}

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

/* Resolution Slider */
.resolution-control {
    margin-block-end: 1.5rem;
    text-align: start;
}

.resolution-control input[type="range"] {
    width: 100%;
    margin-block-start: 0.5rem;
}

/* Buttons */
.download-actions {
    display: flex;
    gap: 0.5rem;
    justify-content: center;
}

.btn-download, .btn-secondary {
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: var(--radius);
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
}

.btn-download {
    background-color: var(--primary-color);
    color: #fff;
    flex: 1;
}

.btn-download:hover {
    background-color: var(--primary-hover);
}

.btn-secondary {
    background-color: #e2e8f0;
    color: var(--text-main);
}

.btn-secondary:hover {
    background-color: #cbd5e1;
}