.valentine{min-height:100vh;display:flex;justify-content:center;align-items:center;overflow:hidden;color:#fff;font-family:Poppins,sans-serif;background:linear-gradient(135deg,#ff758c,#ff7eb3);background-size:400% 400%;animation:gradientBG 15s ease infinite}.valentine.dark{background:linear-gradient(135deg,#1a001f,#3a003d)}@keyframes gradientBG{0%{background-position:0% 50%}50%{background-position:100% 50%}to{background-position:0% 50%}}.container{width:100%;max-width:360px;text-align:center}h1{font-family:Pacifico,cursive;font-size:2.2rem;margin-bottom:10px}.dark-toggle{background:none;border:none;color:#fff;margin-bottom:8px;font-size:.9rem;cursor:pointer}.envelope-container{perspective:1000px;width:220px;height:140px;margin:0 auto 20px}.envelope{width:100%;height:100%;position:relative;transform-style:preserve-3d;transition:transform .8s ease;cursor:pointer}.envelope.open{transform:rotateX(180deg)}.envelope-front,.envelope-back{position:absolute;width:100%;height:100%;border-radius:12px;backface-visibility:hidden}.envelope-front{background:#fff;box-shadow:0 8px 15px #0003}.envelope-back{background:#ffccd6;transform:rotateX(180deg);box-shadow:0 8px 15px #0003}.letter{position:absolute;bottom:10px;left:10px;right:10px;background:#fff;color:#ff4d6d;padding:15px;border-radius:6px;box-shadow:0 5px 10px #0000001a;transform:rotateX(180deg);backface-visibility:hidden}.letter-content{transform:translateY(20px)}.fade-in{opacity:0;animation:fadeSlide .8s forwards}@keyframes fadeSlide{to{opacity:1;transform:translateY(0)}}.question{margin-top:25px}.question p{font-size:1.1rem;margin-bottom:15px}.buttons{display:flex;justify-content:center;gap:15px}button{border:none;padding:12px 20px;border-radius:25px;font-size:1rem;cursor:pointer;transition:all .3s ease}.yes{background:#ff4d6d;color:#fff;box-shadow:0 0 10px #ff4d6d88;animation:pulse 1.5s infinite}.no{background:#ffe3ea;color:#ff4d6d}@keyframes pulse{0%{transform:scale(1)}50%{transform:scale(1.05)}to{transform:scale(1)}}.overlay{position:fixed;inset:0;background:#0006;-webkit-backdrop-filter:blur(4px);backdrop-filter:blur(4px);display:flex;justify-content:center;align-items:center}.popup{background:#fff;color:#ff4d6d;padding:25px;border-radius:20px;text-align:center}.valentine.dark .popup{background:#2b002f;color:#ffb3c6}.heart{position:absolute;bottom:-20px;font-size:20px;animation:float 5s linear infinite}@keyframes float{to{transform:translateY(-120vh);opacity:0}}.petal{position:absolute;bottom:-20px;font-size:18px;animation:floatPetal 6s linear infinite}@keyframes floatPetal{to{transform:translateY(-120vh);opacity:0}}