/* CSS Variables */
:root {
    --color-bg: #0f0f0f;
    --color-surface: #1a1a1a;
    --color-surface-hover: #252525;
    --color-border: #333;
    --color-text: #e0e0e0;
    --color-text-muted: #888;
    --color-primary: #7c3aed;
    --color-primary-hover: #8b5cf6;
    --color-error: #ef4444;
    --color-success: #22c55e;
    --radius: 8px;
    --font-mono: 'SF Mono', 'Monaco', 'Inconsolata', 'Fira Code', monospace;
}

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

/* Base */
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--color-bg);
    color: var(--color-text);
    line-height: 1.6;
    min-height: 100vh;
}

.container {
    max-width: 600px;
    margin: 0 auto;
    padding: 2rem 1rem;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 2rem;
}

h1 {
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 0.25rem;
}

.subtitle {
    color: var(--color-text-muted);
    font-size: 1rem;
}

/* Main */
main {
    flex: 1;
}

/* Form */
#convert-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

/* Drop Zone */
.drop-zone {
    border: 2px dashed var(--color-border);
    border-radius: var(--radius);
    padding: 3rem 2rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s ease;
    background: var(--color-surface);
}

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

.drop-zone.has-file {
    border-color: var(--color-success);
    border-style: solid;
}

.drop-zone-content {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.upload-icon {
    width: 48px;
    height: 48px;
    color: var(--color-text-muted);
}

.drop-zone p {
    color: var(--color-text-muted);
}

.browse-link {
    color: var(--color-primary);
    text-decoration: underline;
}

.file-info {
    font-family: var(--font-mono);
    font-size: 0.875rem;
    color: var(--color-success) !important;
    word-break: break-all;
}

/* Form Groups */
.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-weight: 500;
    font-size: 0.875rem;
}

select {
    appearance: none;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 0.75rem 1rem;
    font-size: 1rem;
    color: var(--color-text);
    cursor: pointer;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%23888' stroke-width='2'%3E%3Cpolyline points='6 9 12 15 18 9'%3E%3C/polyline%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 1rem center;
    padding-right: 2.5rem;
}

select:focus {
    outline: none;
    border-color: var(--color-primary);
}

/* Checkbox */
.checkbox-group label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    cursor: pointer;
}

.checkbox-group input[type="checkbox"] {
    width: 1.25rem;
    height: 1.25rem;
    accent-color: var(--color-primary);
}

.help-text {
    font-size: 0.8rem;
    color: var(--color-text-muted);
    margin-left: 1.75rem;
}

/* Button */
button[type="submit"] {
    background: var(--color-primary);
    color: white;
    border: none;
    border-radius: var(--radius);
    padding: 1rem 1.5rem;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

button[type="submit"]:hover:not(:disabled) {
    background: var(--color-primary-hover);
}

button[type="submit"]:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

button[type="submit"].loading {
    pointer-events: none;
}

.btn-loading {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.spinner {
    width: 20px;
    height: 20px;
    animation: spin 1s linear infinite;
}

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

/* Status */
.status {
    margin-top: 1rem;
    padding: 0.75rem 1rem;
    border-radius: var(--radius);
    font-size: 0.875rem;
    text-align: center;
}

.status:empty {
    display: none;
}

.status.success {
    background: rgba(34, 197, 94, 0.1);
    color: var(--color-success);
    border: 1px solid rgba(34, 197, 94, 0.2);
}

/* Error */
.error {
    margin-top: 1rem;
    padding: 0.75rem 1rem;
    border-radius: var(--radius);
    background: rgba(239, 68, 68, 0.1);
    color: var(--color-error);
    border: 1px solid rgba(239, 68, 68, 0.2);
    font-size: 0.875rem;
}

/* Footer */
footer {
    margin-top: 3rem;
    padding-top: 2rem;
    border-top: 1px solid var(--color-border);
    text-align: center;
    font-size: 0.875rem;
    color: var(--color-text-muted);
}

.format-list {
    font-family: var(--font-mono);
    font-size: 0.75rem;
    margin-top: 0.5rem;
    line-height: 1.8;
}

.footer-links {
    margin-top: 1rem;
}

.footer-links a {
    color: var(--color-primary);
    text-decoration: none;
}

.footer-links a:hover {
    text-decoration: underline;
}

.separator {
    margin: 0 0.5rem;
    color: var(--color-border);
}

/* Responsive */
@media (max-width: 480px) {
    .container {
        padding: 1rem;
    }

    h1 {
        font-size: 2rem;
    }

    .drop-zone {
        padding: 2rem 1rem;
    }
}