.back-btn,.calc-btn{color:#fff;cursor:pointer;transition:.2s}.gst-wrapper{width:100%;max-width:500px;margin:40px auto;padding:16px}.back-btn{background:var(--primary);border:none;padding:10px 14px;border-radius:8px;font-size:15px;margin-bottom:20px;display:flex;align-items:center;gap:6px}.back-btn:hover,.calc-btn:hover{background:var(--primary-700)}.gst-card{background:var(--card-bg);padding:24px;border-radius:14px;box-shadow:var(--shadow)}.gst-card h1{text-align:center;color:var(--text-color);margin-bottom:20px;font-weight:600}.input-group{margin-bottom:18px}.input-group label{display:block;font-size:15px;font-weight:500;margin-bottom:6px;color:var(--text-color)}.input-group input,.input-group select{width:100%;padding:10px 12px;font-size:25px;border-radius:8px;border:1px solid rgba(0,0,0,.15);background:var(--bg-page);color:var(--text-color);outline:0}.calc-btn{width:100%;padding:12px;background:var(--primary);border:none;font-size:16px;border-radius:10px;margin-top:6px}.result-box{margin-top:22px;padding:16px;background:var(--glass);border-radius:10px}.result-box p{font-size:16px;margin-bottom:8px;color:var(--text-color)}@media (max-width:600px){.gst-card{padding:18px}.calc-btn{font-size:15px}}.how-to-use-box{background:var(--card-bg);margin-top:18px;padding:18px;border-radius:var(--radius);box-shadow:var(--shadow);color:var(--text-color)}.how-to-use-box h3{font-size:18px;color:var(--primary);margin-bottom:10px}.how-to-use-box ul{margin-left:18px;color:var(--muted);line-height:1.6}.how-to-use-box ul li{margin-bottom:6px}.how-to-use-box p{color:var(--muted);margin-bottom:8px}