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

:root {
    --bg-primary: #1e1e1e;
    --bg-secondary: #252526;
    --bg-tertiary: #2d2d2d;
    --border-color: #3c3c3c;
    --text-primary: #e0e0e0;
    --text-secondary: #b0b0b0;
    --accent-color: #3b82f6;
    --accent-hover: #2563eb;
    --success-color: #22c55e;
    --danger-color: #ef4444;
}

html, body {
    height: 100%;
    overflow: hidden;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    display: flex;
    flex-direction: column;
}

/* Header */
.app-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 12px 20px;
    background: var(--accent-color);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
}

.app-header h1 {
    font-size: 1.25rem;
    font-weight: 600;
    color: #fff;
}

.header-actions {
    display: flex;
    gap: 8px;
}

/* Buttons */
.btn {
    padding: 8px 16px;
    border: none;
    border-radius: 4px;
    font-size: 0.875rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

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

.btn-primary:hover {
    background: #f0f0f0;
}

.btn-secondary {
    background: rgba(255, 255, 255, 0.15);
    color: #fff;
    border: 1px solid rgba(255, 255, 255, 0.3);
}

.btn-secondary:hover {
    background: rgba(255, 255, 255, 0.25);
}

.btn-add {
    width: 100%;
    padding: 10px;
    background: var(--bg-tertiary);
    border: 1px dashed var(--border-color);
    color: var(--accent-color);
}

.btn-add:hover {
    background: #333;
    border-color: var(--accent-color);
}

.btn-reset {
    width: 100%;
    padding: 10px;
    background: var(--bg-primary);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    margin-top: 15px;
}

.btn-reset:hover {
    background: var(--bg-tertiary);
    border-color: var(--accent-color);
}

/* Main Container */
.app-container {
    display: flex;
    flex: 1;
    overflow: hidden;
    min-height: 0;
}

/* Controls Panel */
.controls-panel {
    width: 340px;
    background: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    overflow-y: auto;
    overflow-x: hidden;
    padding: 15px;
    flex-shrink: 0;
}

/* Preview Panel */
.preview-panel {
    flex: 1;
    display: flex;
    align-items: flex-start;
    justify-content: center;
    padding: 20px;
    background: var(--bg-primary);
    overflow: auto;
}

.preview-container {
    background: #fff;
    border-radius: 8px;
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.3);
    overflow: visible;
    margin-top: 20px;
}

#timelineSvg {
    display: block;
    overflow: visible;
}

/* Responsive */
@media (max-width: 900px) {
    .app-container {
        flex-direction: column;
    }

    .controls-panel {
        width: 100%;
        max-height: 50vh;
        border-right: none;
        border-bottom: 1px solid var(--border-color);
    }

    .preview-panel {
        min-height: 50vh;
    }
}