*{margin:0;padding:0;box-sizing:border-box}
html,body{width:100%;height:100%;overflow:hidden}
body{font-family:'DM Sans',sans-serif;background:radial-gradient(circle at 20% 20%,#253b66 0%,transparent 35%),radial-gradient(circle at 80% 80%,#4a2b61 0%,transparent 40%),linear-gradient(135deg,#090d1a,#12182b);color:white}
.chemistry-bg{position:fixed;inset:0;overflow:hidden;pointer-events:none;z-index:0}
.chem-symbol{position:absolute;color:rgba(255,255,255,.08);font-size:2rem;animation:floatSymbol linear infinite}
.screen{position:fixed;inset:0;display:flex;align-items:center;justify-content:center;padding:20px;opacity:0;visibility:hidden;transform:scale(1.05);transition:opacity .8s ease,transform .8s ease,visibility .8s;z-index:2}
.screen.active{opacity:1;visibility:visible;transform:scale(1)}
.card{width:100%;max-width:430px;padding:42px 30px;text-align:center;background:rgba(255,255,255,.06);border:1px solid rgba(255,255,255,.12);border-radius:28px;backdrop-filter:blur(18px);box-shadow:0 25px 70px rgba(0,0,0,.45),inset 0 1px 0 rgba(255,255,255,.08)}
.small-label{font-size:.7rem;letter-spacing:3px;color:#9ec5ff;margin-bottom:25px;font-weight:600}
h1,h2{font-family:'Playfair Display',serif}
h1{font-size:clamp(2rem,7vw,3rem);line-height:1.15;margin-bottom:20px}
h1 span{display:block;color:#a9c7ff;margin-top:8px}
h2{font-size:1.8rem;margin-top:25px;margin-bottom:12px}
p{color:rgba(255,255,255,.68);line-height:1.7;font-size:.95rem}
.molecule{font-size:4.5rem;margin-bottom:20px;animation:spinFloat 6s ease-in-out infinite;filter:drop-shadow(0 0 20px rgba(110,160,255,.6))}
button{border:none;margin-top:30px;padding:14px 25px;border-radius:50px;font-family:'DM Sans',sans-serif;font-size:.95rem;font-weight:600;color:white;cursor:pointer;background:linear-gradient(135deg,#5b8cff,#8d5cff);box-shadow:0 10px 30px rgba(91,140,255,.35);transition:.3s}
button:hover{transform:translateY(-3px);box-shadow:0 15px 40px rgba(91,140,255,.5)}
button:active{transform:scale(.95)}
.hidden{display:none}
.flask-container{position:relative;width:180px;height:220px;margin:10px auto}
.flask-neck{position:absolute;width:45px;height:75px;top:0;left:50%;transform:translateX(-50%);border-left:4px solid rgba(210,235,255,.8);border-right:4px solid rgba(210,235,255,.8);border-radius:5px}
.flask-body{position:absolute;width:160px;height:140px;bottom:0;left:50%;transform:translateX(-50%);border:4px solid rgba(210,235,255,.8);border-top:none;border-radius:20px 20px 40px 40px;overflow:hidden;box-shadow:0 0 35px rgba(110,170,255,.25)}
.liquid{position:absolute;bottom:0;width:100%;height:25%;background:linear-gradient(135deg,#7c5cff,#4bbcff);box-shadow:0 0 30px rgba(90,120,255,.8);animation:liquidGlow 2s infinite alternate}
.bubble{position:absolute;width:12px;height:12px;border-radius:50%;background:#8fc9ff;opacity:0;box-shadow:0 0 15px #8fc9ff;animation:bubbleRise 3s infinite}
.b1{left:35%;bottom:30%}.b2{left:55%;bottom:20%;animation-delay:.8s}.b3{left:65%;bottom:35%;animation-delay:1.5s}.b4{left:45%;bottom:15%;animation-delay:2s}
.reaction-active .liquid{animation:reactionLiquid 2s ease-in-out infinite}.reaction-active .flask-body{box-shadow:0 0 60px rgba(170,90,255,.8)}
.teacher-icon{font-size:4rem;margin-bottom:20px;animation:teacherFloat 4s ease-in-out infinite}
.message{display:flex;flex-direction:column;gap:18px;margin-top:25px}
.thank-you{margin-top:30px;font-family:'Playfair Display',serif;font-size:1.7rem;color:#ffc6dc;text-shadow:0 0 25px rgba(255,120,180,.5)}
.signature{margin-top:15px;font-size:.8rem;color:rgba(255,255,255,.45)}
@keyframes floatSymbol{0%{transform:translateY(110vh) rotate(0);opacity:0}10%{opacity:.12}90%{opacity:.12}100%{transform:translateY(-20vh) rotate(360deg);opacity:0}}
@keyframes spinFloat{0%,100%{transform:translateY(0) rotate(0)}50%{transform:translateY(-10px) rotate(10deg)}}
@keyframes bubbleRise{0%{transform:translateY(0) scale(.5);opacity:0}30%{opacity:1}100%{transform:translateY(-130px) scale(1.4);opacity:0}}
@keyframes liquidGlow{from{filter:brightness(1)}to{filter:brightness(1.5)}}
@keyframes reactionLiquid{0%,100%{height:30%;filter:hue-rotate(0)}50%{height:65%;filter:hue-rotate(80deg)}}
@keyframes teacherFloat{0%,100%{transform:translateY(0)}50%{transform:translateY(-10px)}}