:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --bg-gradient: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
    --glass-bg: rgba(255, 255, 255, 0.7);
    --glass-border: rgba(255, 255, 255, 0.5);
    --text-main: #1f2937;
    --text-muted: #6b7280;
    --shadow: 0 8px 32px 0 rgba(31, 38, 135, 0.1);
    --ball-shadow: 0 4px 10px rgba(0, 0, 0, 0.2);
    --card-bg: white;
    --placeholder-bg: rgba(0, 0, 0, 0.05);
    }
    
  * {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Pretendard', sans-serif;
    transition: background 0.3s ease, background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease, box-shadow 0.3s ease;
    }
    
    body {
    background: var(--bg-gradient);
    background-attachment: fixed;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 20px;
    }
    
    .app-container {
    background: var(--glass-bg);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border: 1px solid var(--glass-border);
    border-radius: 24px;
    width: 100%;
    max-width: 600px;
    padding: 40px;
    box-shadow: var(--shadow);
    }
    
    header {
    text-align: center;
    margin-bottom: 40px;
    }
    
    header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--text-main);
    letter-spacing: -0.025em;
    }
    
    header h1 span {
    color: var(--primary-color);
    }
    
    header p {
    color: var(--text-muted);
    margin-top: 8px;
    }
    
    .drawing-board {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 30px;
    }
    
    .ball-container {
    display: flex;
    justify-content: center;
    flex-direction: column;
    align-items: center;
    gap: 15px;
    min-height: 80px;
    }
    
    .placeholder-balls {
    display: flex;
    gap: 15px;
    }
    
    .placeholder-ball {
    width: 60px;
    height: 60px;
    border-radius: 50%;
    background: var(--placeholder-bg);
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 1.2rem;
    color: var(--text-muted);
    border: 2px dashed var(--glass-border);
    }
    
    .actions {
    display: flex;
    gap: 12px;
    width: 100%;
    }
    
    button {
    flex: 1;
    padding: 16px 24px;
    border-radius: 12px;
    font-size: 1rem;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s ease;
    border: none;
    }
    
    .primary-btn {
    background: var(--primary-color);
    color: white;
    box-shadow: 0 4px 14px rgba(99, 102, 241, 0.4);
    }
    
    .primary-btn:hover {
    background: var(--primary-hover);
    transform: translateY(-2px);
    }
    
    .primary-btn:active {
    transform: translateY(0);
    }
    
    .secondary-btn {
    background: var(--card-bg);
    color: var(--text-main);
    border: 1px solid var(--glass-border);
    }
    
    .secondary-btn:hover {
    background: rgba(128, 128, 128, 0.1);
    }
    
    .history-section {
    margin-top: 50px;
    border-top: 1px solid var(--glass-border);
    padding-top: 30px;
    }
    
    .history-section h2 {
    font-size: 1.25rem;
    color: var(--text-main);
    margin-bottom: 20px;
    }
    
    .history-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 12px;
    max-height: 200px;
    overflow-y: auto;
    padding-right: 8px;
    }
    
    .history-item {
    background: var(--card-bg);
    padding: 12px 16px;
    border-radius: 12px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    animation: slideIn 0.3s ease-out;
    }
    
    .history-balls {
    display: flex;
    gap: 6px;
    }
    
    .history-ball-mini {
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 0.75rem;
    font-weight: 700;
    color: white;
    }
    
    .history-date {
    font-size: 0.8rem;
    color: var(--text-muted);
    }
    
    .empty-history {
    text-align: center;
    color: var(--text-muted);
    font-style: italic;
    padding: 20px 0;
    }
    
    footer {
    text-align: center;
    margin-top: 40px;
    color: var(--text-muted);
    font-size: 0.875rem;
    }
    
    @keyframes slideIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
    }
    
  /* Custom Scrollbar */
    .history-list::-webkit-scrollbar {
    width: 6px;
    }
    .history-list::-webkit-scrollbar-track {
    background: transparent;
    }
    .history-list::-webkit-scrollbar-thumb {
    background: #d1d5db;
    border-radius: 10px;
    }
    
    @media (max-width: 480px) {
    .app-container {
        padding: 24px;
    }
    header h1 {
        font-size: 2rem;
    }
    }