:root {
    --bg: #ffffff;
    --bg-subtle: #f8fafc;
    --bg-surface: #ffffff;
    --border: #e2e8f0;
    --border-hover: #cbd5e1;
    --border-focus: #0f172a;
    
    --text-main: #0f172a;
    --text-muted: #64748b;
    --text-faint: #94a3b8;
    
    --primary: #0f172a;
    --primary-hover: #1e293b;
    --primary-text: #ffffff;
    
    --radius: 8px;
    --font-sans: 'Pretendard', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans KR', sans-serif;
    --font-mono: 'JetBrains Mono', 'Fira Code', Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --bg: #09090b;
        --bg-subtle: #141417;
        --bg-surface: #18181b;
        --border: #27272a;
        --border-hover: #3f3f46;
        --border-focus: #fafafa;
        
        --text-main: #fafafa;
        --text-muted: #a1a1aa;
        --text-faint: #71717a;
        
        --primary: #fafafa;
        --primary-hover: #e4e4e7;
        --primary-text: #09090b;
    }
}

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

body {
    background-color: var(--bg);
    color: var(--text-main);
    font-family: var(--font-sans);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 3rem 1.5rem;
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

.container {
    width: 100%;
    max-width: 860px;
    margin: 0 auto;
}

/* Header */
.header {
    margin-bottom: 2rem;
}

.title {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    color: var(--text-main);
    margin-bottom: 0.35rem;
}

.subtitle {
    font-size: 0.925rem;
    color: var(--text-muted);
}

/* Card */
.card {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
}

/* Segmented Control / Tabs */
.tabs {
    display: flex;
    background: var(--bg-subtle);
    border-bottom: 1px solid var(--border);
    padding: 4px;
    gap: 4px;
}

.tab-btn {
    flex: 1;
    padding: 0.55rem 1rem;
    background: transparent;
    border: none;
    border-radius: 6px;
    color: var(--text-muted);
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.15s ease;
}

.tab-btn:hover {
    color: var(--text-main);
}

.tab-btn.active {
    background: var(--bg-surface);
    color: var(--text-main);
    font-weight: 600;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.05);
}

/* Content Area */
.tab-content {
    display: none;
    padding: 1.25rem;
}

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

/* Toolbar */
.toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 0.75rem;
}

.btn-ghost {
    background: transparent;
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-muted);
    font-family: inherit;
    font-size: 0.8rem;
    padding: 0.35rem 0.65rem;
    cursor: pointer;
    transition: all 0.15s ease;
}

.btn-ghost:hover {
    background: var(--bg-subtle);
    color: var(--text-main);
    border-color: var(--border-hover);
}

.toolbar-group {
    display: flex;
    gap: 0.4rem;
}

/* Textarea */
.textarea {
    width: 100%;
    height: 360px;
    padding: 1rem;
    background: var(--bg-subtle);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-main);
    font-family: var(--font-mono);
    font-size: 0.875rem;
    line-height: 1.6;
    resize: vertical;
    outline: none;
    transition: border-color 0.15s ease;
}

.textarea:focus {
    border-color: var(--border-focus);
    background: var(--bg-surface);
}

.textarea::placeholder {
    color: var(--text-faint);
}

/* Dropzone */
.dropzone {
    border: 1px dashed var(--border);
    border-radius: 6px;
    background: var(--bg-subtle);
    padding: 3rem 1.5rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.15s ease;
}

.dropzone:hover, .dropzone.dragover {
    border-color: var(--border-focus);
    background: var(--bg-surface);
}

.dropzone-text {
    font-size: 0.925rem;
    font-weight: 500;
    color: var(--text-main);
    margin-bottom: 0.25rem;
}

.dropzone-hint {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.file-selected {
    display: none;
    margin-top: 1rem;
    padding: 0.5rem 0.85rem;
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 0.85rem;
    color: var(--text-main);
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.file-selected.active {
    display: inline-flex;
}

.file-clear-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 0.9rem;
    margin-left: 0.25rem;
}

.file-clear-btn:hover {
    color: #ef4444;
}

/* Footer / Controls */
.footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 1rem 1.25rem;
    background: var(--bg-subtle);
    border-top: 1px solid var(--border);
    flex-wrap: wrap;
    gap: 0.75rem;
}

.controls {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    flex-wrap: wrap;
}

.control-item {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    font-size: 0.825rem;
    color: var(--text-muted);
}

.input, .select {
    background: var(--bg-surface);
    border: 1px solid var(--border);
    border-radius: 6px;
    color: var(--text-main);
    font-family: inherit;
    font-size: 0.825rem;
    padding: 0.45rem 0.65rem;
    outline: none;
    transition: border-color 0.15s ease;
}

.input:focus, .select:focus {
    border-color: var(--border-focus);
}

.btn-primary {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    background: var(--primary);
    color: var(--primary-text);
    border: none;
    border-radius: 6px;
    font-family: inherit;
    font-size: 0.875rem;
    font-weight: 600;
    padding: 0.55rem 1.25rem;
    cursor: pointer;
    transition: background-color 0.15s ease;
}

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

.btn-primary:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* Minimal Spinner */
.spinner {
    display: none;
    width: 14px;
    height: 14px;
    border: 2px solid rgba(128, 128, 128, 0.3);
    border-radius: 50%;
    border-top-color: currentColor;
    animation: spin 0.6s linear infinite;
}

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

.btn-primary.loading .spinner {
    display: inline-block;
}

/* Toast */
.toast-container {
    position: fixed;
    bottom: 1.5rem;
    right: 1.5rem;
    z-index: 100;
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.toast {
    background: var(--text-main);
    color: var(--bg);
    padding: 0.65rem 1rem;
    border-radius: 6px;
    font-size: 0.825rem;
    font-weight: 500;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    animation: toastIn 0.2s ease-out forwards;
}

@keyframes toastIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}