.form-group { margin-bottom: 20px; }
        label { display: block; font-size: 14px; font-weight: 600; margin-bottom: 8px; color: var(--text-main); }
        
        input, select { width: 100%; padding: 12px; border: 2px solid var(--border-color); border-radius: 8px; font-size: 16px; transition: border-color 0.2s; outline: none; }
        input:focus { border-color: var(--primary-color); }

        .tabs { display: flex; gap: 10px; margin-bottom: 20px; background: #f1f5f9; padding: 5px; border-radius: 10px; }
        .tab-btn { flex: 1; padding: 10px; border: none; background: transparent; border-radius: 8px; cursor: pointer; font-weight: 500; transition: 0.2s; font-size: 14px; }
        .tab-btn.active { background: var(--bg-light); box-shadow: 0 2px 5px rgba(0,0,0,0.05); color: var(--primary-color); }

        .gst-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 8px; margin-bottom: 10px; }
        .gst-btn { padding: 10px; border: 1px solid var(--border-color); background: white; border-radius: 8px; cursor: pointer; font-size: 14px; transition: 0.2s; }
        .gst-btn.active { background: var(--primary-color); color: white; border-color: var(--primary-color); }

        .results-box { background: #f8fafc; border-radius: 12px; padding: 20px; margin-top: 25px; border: 1px dashed var(--border-color); }
        .result-row { display: flex; justify-content: space-between; margin-bottom: 12px; font-size: 15px; }
        .result-row.total { margin-top: 15px; padding-top: 15px; border-top: 2px solid var(--border-color); font-weight: 700; font-size: 18px; color: var(--primary-color); }
        .label-muted { color: var(--text-muted); font-weight: 400; }

        .actions { display: flex; gap: 10px; margin-top: 20px; }
        .btn { flex: 1; padding: 12px; border: none; border-radius: 8px; font-weight: 600; cursor: pointer; transition: 0.2s; display: flex; align-items: center; justify-content: center; gap: 8px; }
        .btn-clear { background: #fee2e2; color: #ef4444; }
        .btn-copy { background: var(--primary-color); color: white; }
        .btn-copy:hover { background: var(--primary-hover); }

        .custom-gst-wrap { display: none; margin-top: 10px; }
        .custom-gst-wrap.show { display: block; }

        @media (max-width: 480px) {
            .gst-grid { grid-template-columns: repeat(2, 1fr); }
        }