*{box-sizing:border-box;margin:0;padding:0}body{background:#0b0e1a;display:flex;justify-content:center;align-items:center;min-height:100vh;font-family:Nunito,sans-serif;overflow:hidden;touch-action:none}#back-link{position:fixed;top:12px;left:12px;color:#fff9;text-decoration:none;font-size:.85rem;font-family:Inter,sans-serif;z-index:100;background:#0006;padding:6px 12px;border-radius:20px;transition:color .2s}#back-link:hover{color:#fff}#mute-btn{position:fixed;top:12px;right:12px;background:#0006;border:none;color:#fff;font-size:1.2rem;padding:6px 10px;border-radius:20px;cursor:pointer;z-index:100}#game-wrapper{position:relative;width:min(480px,100vw,75vh);aspect-ratio:480 / 640;background:linear-gradient(160deg,#1b2240,#0b0e1a);border-radius:12px;overflow:hidden}#hud{position:absolute;top:10px;left:0;right:0;display:flex;justify-content:space-between;padding:0 16px;color:#fff;font-family:Inter,sans-serif;font-weight:700;font-size:.85rem;pointer-events:none;text-shadow:0 1px 3px rgba(0,0,0,.6);z-index:5}#score-box span{color:#ffd32a}#combo-box span{color:#ff9f43}#lives-box span{color:#ff6b6b}#level-box span{color:#1dd1a1}#timer-bar-wrap{position:absolute;top:40px;left:16px;right:16px;height:10px;background:#ffffff1a;border-radius:6px;overflow:hidden;z-index:5}#timer-bar{height:100%;width:100%;background:linear-gradient(90deg,#1dd1a1,#54a0ff);border-radius:6px;transform-origin:left;transition:width .1s linear,background-color .2s}#timer-bar.warn{background:linear-gradient(90deg,#feca57,#ff9f43)}#timer-bar.danger{background:linear-gradient(90deg,#ff6b6b,#ee5253)}#game-area{position:absolute;top:0;right:0;bottom:0;left:0;display:flex;flex-direction:column;align-items:center;justify-content:center;padding:80px 24px 24px;gap:24px}#equation{font-family:Nunito,sans-serif;font-weight:900;font-size:3rem;color:#fff;text-align:center;text-shadow:0 2px 8px rgba(0,0,0,.5);min-height:4rem}#feedback{font-family:Nunito,sans-serif;font-weight:900;font-size:1.4rem;min-height:1.8rem;text-align:center;transition:opacity .2s}#feedback.correct{color:#1dd1a1}#feedback.wrong{color:#ff6b6b}#choices{display:grid;grid-template-columns:repeat(2,1fr);gap:16px;width:100%;max-width:360px}.choice-btn{font-family:Nunito,sans-serif;font-weight:900;font-size:1.8rem;color:#fff;background:#ffffff14;border:2px solid rgba(255,255,255,.15);border-radius:16px;padding:20px 8px;cursor:pointer;transition:transform .1s,background-color .15s,border-color .15s;-webkit-tap-highlight-color:transparent}.choice-btn:hover{background:#ffffff29;border-color:#ffffff4d}.choice-btn:active{transform:scale(.96)}.choice-btn.correct{background:#1dd1a159;border-color:#1dd1a1}.choice-btn.wrong{background:#ff6b6b59;border-color:#ff6b6b}.choice-btn:disabled{cursor:default}.overlay{position:absolute;top:0;right:0;bottom:0;left:0;display:flex;align-items:center;justify-content:center;background:#000000bf;border-radius:12px;z-index:20}.overlay-box{text-align:center;color:#fff;padding:32px 40px;background:#141428f2;border-radius:20px;border:2px solid rgba(255,255,255,.1);box-shadow:0 20px 60px #0009;max-width:90%}.overlay-emoji{font-size:4rem;margin-bottom:12px}.overlay-box h1{font-size:1.8rem;font-weight:900;margin-bottom:12px;color:#ffd32a}.overlay-box p{font-size:1rem;color:#fffc;margin-bottom:8px;line-height:1.6}.hint-row{display:flex;flex-direction:column;gap:4px;font-size:.9rem;margin:14px 0;color:#ffffffb3}.hint-small{font-size:.85rem;color:#ffffff80}#best-score-row,#stats-row,#stats-row2{color:#fff9;font-size:.9rem}.btn-primary{margin-top:20px;background:linear-gradient(135deg,#54a0ff,#00d2d3);color:#fff;font-family:Nunito,sans-serif;font-size:1.2rem;font-weight:900;border:none;padding:14px 40px;border-radius:50px;cursor:pointer;box-shadow:0 4px 20px #54a0ff66;transition:transform .15s,box-shadow .15s}.btn-primary:hover{transform:translateY(-2px);box-shadow:0 8px 30px #54a0ff99}.btn-primary:active{transform:translateY(0)}