.app-bg{min-height:100vh;background:linear-gradient(to bottom right,#d9ead3,#e3f0d0,#f6f9f1);display:flex;align-items:center;justify-content:center;flex-direction:column;transition:background .8s ease}.intro-screen{text-align:center}.intro-title{font-size:3rem;font-weight:700;color:#388e3c;margin-bottom:.5rem}.intro-subtitle{font-size:1.1rem;color:#444;margin-bottom:1.8rem}.start-btn{background:linear-gradient(135deg,#81c784,#66bb6a);border:none;color:#fff;font-size:1.1rem;font-weight:600;padding:.8rem 2rem;border-radius:30px;cursor:pointer;box-shadow:0 4px 15px #66bb6a66;transition:transform .2s ease,box-shadow .3s ease}.start-btn:hover{transform:scale(1.05);box-shadow:0 6px 20px #66bb6a99}.intro-subtext{color:#555;font-size:.95rem;text-align:center;margin-bottom:1.2rem}