:root{--primary-color: #00529b;--secondary-color: #f7f7f7;--accent-color: #4caf50;--danger-color: #f44336;--text-color: #333;--border-color: #ddd;--shadow-color: rgba(0, 0, 0, .1);--font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif}body{font-family:var(--font-family);background-color:var(--secondary-color);color:var(--text-color);margin:0;padding:20px;line-height:1.6}.app-container{max-width:1000px;margin:auto;background:#fff;padding:25px;border-radius:10px;box-shadow:0 4px 12px var(--shadow-color)}h1{color:var(--primary-color);border-bottom:2px solid var(--border-color);padding-bottom:10px;margin-top:0}.progress-container{margin-bottom:20px}.progress-bar{width:100%;background-color:var(--border-color);border-radius:5px;overflow:hidden}.progress-bar-fill{height:20px;background-color:var(--accent-color);text-align:center;line-height:20px;color:#fff;border-radius:5px;transition:width .5s ease-in-out;font-weight:700}.topic-section{background:#fafafa;border:1px solid var(--border-color);border-radius:8px;padding:20px;margin-bottom:20px}.topic-header{display:flex;justify-content:space-between;align-items:center;cursor:pointer;-webkit-user-select:none;user-select:none}.topic-header h2{margin:0;color:var(--primary-color)}.toggle-icon{font-size:1.8rem;font-weight:700;color:var(--primary-color)}.topic-questions{list-style-type:none;padding:0;margin-top:15px}.question-item{display:flex;align-items:center;padding:12px 5px;border-bottom:1px solid #eee}.question-item.completed .question-text{text-decoration:line-through;color:#888}.question-text{flex-grow:1;margin:0 15px}.difficulty{font-weight:700;padding:3px 8px;border-radius:12px;font-size:.8em;min-width:60px;text-align:center}.difficulty-Easy{background-color:#e8f5e9;color:#388e3c}.difficulty-Medium{background-color:#fff3e0;color:#f57c00}.difficulty-Hard{background-color:#ffebee;color:#d32f2f}input[type=checkbox]{width:18px;height:18px;cursor:pointer;margin-right:10px}.filter-controls{display:flex;justify-content:flex-end;align-items:center;gap:20px;margin-bottom:20px;flex-wrap:wrap;padding:10px;background-color:#f8f9fa;border-radius:8px}.filter-group{display:flex;align-items:center;gap:8px}.filter-group label{font-weight:700;color:var(--primary-color)}.filter-group select{padding:8px;border-radius:5px;border:1px solid var(--border-color);font-size:1em;font-family:var(--font-family)}.add-item-form{display:flex;gap:10px;margin-top:20px;border-top:1px solid var(--border-color);padding-top:20px}.add-item-form input[type=text]{flex-grow:1;padding:8px;border-radius:5px;border:1px solid var(--border-color);font-size:1em}.add-item-form select{padding:8px;border-radius:5px;border:1px solid var(--border-color);font-size:1em}.add-item-form button{padding:8px 15px;border-radius:5px;border:none;color:#fff;cursor:pointer;font-size:1em;transition:background-color .3s ease}.btn-add{background-color:var(--accent-color)}.btn-add:hover{background-color:#45a049}