:root {
    --bg-color: #1a1a1a;
    --surface-color: #2c2c2c;
    --primary-text: #f0f0f0;
    --secondary-text: #a0a0a0;
    --accent-color: #007aff;
    --accent-hover: #0056b3;
    --border-color: #444;
    --shadow-color: rgba(0, 0, 0, 0.2);
    --border-radius: 8px;
}
* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body {
    font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--primary-text);
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 100vh;
    padding: 2rem 1rem;
}
.app-container {
    width: 100%;
    max-width: 900px;
}
.app-header {
    text-align: center;
    margin-bottom: 2rem;
}
.app-header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
}
.app-header p {
    color: var(--secondary-text);
    font-size: 1.1rem;
}
.generator-core {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
}
@media (min-width: 800px) {
    .generator-core {
        grid-template-columns: 1fr 320px;
    }
}
.controls-panel, .preview-panel {
    background-color: var(--surface-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
}
.controls-panel {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}
.control-group {
    display: flex;
    flex-direction: column;
}
.control-group label {
    margin-bottom: 0.5rem;
    color: var(--secondary-text);
    font-size: 0.9rem;
    font-weight: 500;
}
textarea, select, input[type="file"] {
    width: 100%;
    padding: 0.75rem;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--primary-text);
    border-radius: 6px;
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}
textarea:focus, select:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(0, 122, 255, 0.3);
}
input[type="color"] {
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    width: 100%;
    height: 40px;
    background-color: transparent;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    cursor: pointer;
}
input[type="color"]::-webkit-color-swatch {
    border: none;
    border-radius: 5px;
}
input[type="color"]::-moz-color-swatch {
    border: none;
    border-radius: 5px;
}
.inline-controls {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}
.slider-group {
    display: flex;
    align-items: center;
    gap: 1rem;
}
#qr-size {
    flex-grow: 1;
}
input[type="file"] {
    display: none;
}
.file-label {
    width: 100%;
    padding: 0.75rem;
    background-color: var(--bg-color);
    border: 1px dashed var(--border-color);
    border-radius: 6px;
    text-align: center;
    cursor: pointer;
    transition: background-color 0.2s, border-color 0.2s;
}
.file-label:hover {
    background-color: #333;
    border-color: var(--secondary-text);
}
.text-button {
    background: none;
    border: none;
    color: var(--accent-color);
    font-size: 0.9rem;
    cursor: pointer;
    text-align: right;
    margin-top: 0.5rem;
    transition: color 0.2s;
}
.text-button:hover {
    color: var(--accent-hover);
}
.hidden {
    display: none;
}
.action-button {
    padding: 0.8rem 1rem;
    font-size: 1rem;
    font-weight: 600;
    color: #fff;
    background-color: var(--accent-color);
    border: none;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s;
}
.action-button:hover {
    background-color: var(--accent-hover);
}
.preview-panel {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
#qr-code-container {
    background-color: #fff;
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    box-shadow: 0 4px 10px var(--shadow-color);
}
#qr-code-container canvas,
#qr-code-container svg {
    display: block;
    width: 100%;
    height: 100%;
}
.preview-panel p {
    color: var(--secondary-text);
    font-weight: 500;
}
.app-footer {
    text-align: center;
    margin-top: 3rem;
    color: var(--secondary-text);
}
.app-footer a {
    color: var(--accent-color);
    text-decoration: none;
}
.app-footer a:hover {
    text-decoration: underline;
}
.app-footer .separator {
    margin: 0 0.5rem;
    color: var(--border-color);
}