:root{--bg:#f4f6f8;--card:#fff;--text:#16212b;--muted:#6f7b86;--line:#e3e8ed;--navy:#14263b;--teal:#2f7f78;--teal-soft:#e8f3f1;--gold:#d6a24a;--gold-soft:#fff5df}*{box-sizing:border-box}body{margin:0;background:#e8edf1;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Noto Sans KR",sans-serif;color:var(--text);-webkit-font-smoothing:antialiased}button{font-family:inherit}.app{width:min(100%,430px);min-height:100vh;margin:auto;background:linear-gradient(180deg,#fafcfd 0%,var(--bg) 28%,#f5f6f7 100%);padding-bottom:86px;box-shadow:0 0 60px rgba(18,38,58,.13)}header{padding:20px 20px 10px;display:flex;justify-content:space-between;align-items:center}.brand{font-size:12px;font-weight:950;letter-spacing:.16em;color:var(--navy);display:flex;align-items:center;gap:8px}.brand:before{content:"♥";width:25px;height:25px;border-radius:8px;display:grid;place-items:center;background:var(--navy);color:#fff;font-size:11px}.avatar{width:40px;height:40px;border-radius:14px;background:linear-gradient(145deg,var(--navy),var(--teal));color:#fff;display:grid;place-items:center;font-size:12px;font-weight:950}main{padding:8px 19px 30px}.screen{display:none}.screen.active{display:block}.kicker{font-size:10.5px;font-weight:950;letter-spacing:.12em;color:var(--teal);text-transform:uppercase}h1{font-size:30px;line-height:1.12;letter-spacing:-.035em;margin:8px 0 6px;color:var(--navy)}h2{font-size:24px;line-height:1.25;margin:10px 0}h3{font-size:17px;margin:6px 0}.sub{font-size:15px;color:var(--muted);line-height:1.65}.hero{position:relative;overflow:hidden;background:radial-gradient(circle at 88% 15%,rgba(214,162,74,.3),transparent 25%),linear-gradient(145deg,#13263a 0%,#1f4252 62%,#2e766f 120%);color:#fff;border-radius:26px;padding:24px 22px;margin-top:18px;box-shadow:0 18px 50px rgba(18,38,58,.14)}.hero .kicker{color:#b9ddd8}.hero h2{color:#fff}.hero .sub{color:rgba(255,255,255,.78)}.levels{display:flex;gap:6px;margin-top:15px;overflow:auto}.level{flex:0 0 auto;padding:8px 11px;border-radius:999px;border:1px solid rgba(255,255,255,.22);font-size:10.5px;font-weight:900;color:rgba(255,255,255,.72)}.level.on{background:#fff;color:var(--navy)}.section{display:flex;align-items:center;gap:9px;font-size:16px;font-weight:950;color:var(--navy);margin:25px 0 11px}.section:before{content:"";width:4px;height:17px;border-radius:99px;background:linear-gradient(var(--teal),var(--gold))}.topic,.panel,.dialogue,.challenge-card,.baseline{background:#fff;border:1px solid var(--line);border-radius:20px;box-shadow:0 7px 22px rgba(18,38,58,.05)}.topic{padding:17px 43px 17px 20px;margin-top:10px;cursor:pointer;position:relative}.topic:before{content:"";position:absolute;left:0;top:0;bottom:0;width:5px;background:var(--teal);border-radius:20px 0 0 20px}.topic:after{content:"›";position:absolute;right:16px;top:50%;transform:translateY(-50%);width:27px;height:27px;border-radius:50%;display:grid;place-items:center;background:#f0f4f6;color:var(--navy);font-size:19px}.topic b{font-size:15.5px;color:var(--navy)}.topic span{font-size:12.5px;color:var(--muted);line-height:1.5}.num{font-size:10px;font-weight:900;color:var(--teal);background:var(--teal-soft);border-radius:999px;padding:5px 7px;display:inline-block;margin-bottom:7px}button{border:0;border-radius:14px;padding:12px 14px;font-size:14px;font-weight:900;cursor:pointer}.dark{background:linear-gradient(135deg,var(--navy),#213f5d);color:#fff}.soft{background:#edf2f4;color:var(--navy);border:1px solid #e0e7eb}.wide{width:100%;margin-top:10px}.back{background:transparent;color:var(--teal);padding:4px 0 12px}.flip{perspective:1000px;cursor:pointer}.flip-inner{position:relative;min-height:245px;transition:transform .5s cubic-bezier(.2,.7,.2,1);transform-style:preserve-3d}.flip.flipped .flip-inner{transform:rotateY(180deg)}.flip-face{position:absolute;inset:0;backface-visibility:hidden;-webkit-backface-visibility:hidden;border-radius:22px;padding:19px;border:1px solid #dde6ea;box-shadow:0 9px 25px rgba(18,38,58,.06);display:flex;flex-direction:column;pointer-events:none}.flip-front{background:linear-gradient(155deg,#fffdf8,#fff);border-top:5px solid var(--gold)}.flip-back{transform:rotateY(180deg);background:linear-gradient(155deg,var(--teal-soft),#fff);border-top:5px solid var(--teal)}.flip:not(.flipped) .flip-front,.flip.flipped .flip-back{pointer-events:auto}.flip-back button{position:relative;z-index:5;pointer-events:auto}.flip-label{font-size:10.5px;font-weight:950;letter-spacing:.08em;color:var(--teal);text-transform:uppercase}.flip-ko{margin:auto 0;font-size:21px;line-height:1.52;font-weight:900;letter-spacing:-.025em;color:var(--navy)}.flip-en{margin:auto 0 8px;font-size:19px;line-height:1.5;font-weight:900;color:var(--navy)}.flip-ko-small{font-size:12.5px;color:var(--muted);line-height:1.5}.flip-hint{margin-top:auto;padding:10px 12px;border-radius:13px;background:var(--gold-soft);color:#76551b;text-align:center;font-size:12px;font-weight:850}.baseline{padding:16px;background:#f6f8f9}.tone{font-size:10.5px;font-weight:950;letter-spacing:.08em;color:var(--teal);text-transform:uppercase;margin-bottom:8px}.base-sentence{font-size:15px;line-height:1.55;font-weight:800;color:var(--navy)}.upgrade-card{margin-top:9px;background:linear-gradient(155deg,var(--teal-soft),#fff);border:1px solid #d7e9e6;border-radius:20px;padding:17px;box-shadow:0 7px 22px rgba(18,38,58,.05)}.upgrade-head{display:flex;justify-content:space-between;gap:10px;align-items:center}.badge{font-size:9.5px;font-weight:950;letter-spacing:.08em;background:var(--navy);color:#fff;padding:6px 8px;border-radius:999px}.up-en{font-size:19px;line-height:1.5;font-weight:900;color:var(--navy);margin:14px 0 4px}.up-ko{font-size:12.5px;line-height:1.5;color:var(--muted)}.note{margin-top:11px;padding:10px 11px;border-radius:12px;background:var(--gold-soft);font-size:11.5px;line-height:1.5;color:#76551b}.actions{display:grid;grid-template-columns:1fr 1fr;gap:7px;margin-top:11px}.expr-flip{margin-top:10px}.expr-flip .flip-inner{min-height:205px}.expr-flip .flip-ko{font-size:19px}.expr-flip .flip-en{font-size:18px}.dialogue{padding:8px 14px;background:linear-gradient(180deg,#fff,#f9fbfc)}.line{padding:12px 0;border-bottom:1px solid #edf1f3}.line:last-child{border-bottom:0}.speaker{font-size:10.5px;font-weight:950;color:var(--teal);margin-bottom:4px;text-transform:uppercase}.line-en{font-size:14.5px;line-height:1.6;font-weight:650;color:var(--navy)}.line-ko{font-size:12px;line-height:1.5;color:#8a969f;margin-top:3px}.challenge-card{padding:16px;margin-top:10px}.challenge-top{display:flex;justify-content:space-between;align-items:center}.challenge-num{font-size:10px;color:#8a969f;font-weight:900}.challenge-ko{font-size:15px;line-height:1.62;font-weight:800;color:var(--navy);margin:10px 0}.challenge-answer{display:none;margin-top:10px;padding:12px 13px;border-radius:14px;background:var(--teal-soft);border:1px solid #d5e8e5}.challenge-answer.show{display:block}.challenge-en{font-size:14px;line-height:1.58;font-weight:850;color:var(--navy)}.challenge-note{font-size:11.5px;color:var(--muted);margin-top:5px;line-height:1.45}.panel{padding:17px}.rolebox{background:linear-gradient(180deg,#fff,#f9fbfc)}.role-line{padding:12px;border-radius:14px;background:#f3f6f8;margin-top:9px;font-size:13px;line-height:1.55}.role-line.you{background:var(--teal-soft)}.modebar{display:grid;grid-template-columns:1fr 1fr;gap:7px;margin:10px 0}.modebar button.selected{background:linear-gradient(135deg,var(--navy),var(--teal));color:#fff}.modebar span{font-size:10px}.hintbox{padding:11px;border-radius:12px;background:var(--gold-soft);font-size:12px;line-height:1.5;color:#76551b;margin-top:9px}.gpt-panel{background:linear-gradient(180deg,#fff,#fbfcfd)}.gpt-head{display:flex;justify-content:space-between;align-items:center;gap:12px}.gpt-badge{width:46px;height:46px;border-radius:15px;display:grid;place-items:center;background:linear-gradient(145deg,var(--navy),var(--teal));color:#fff;font-size:11px;font-weight:950}.gpt-desc{font-size:13px;line-height:1.6;color:var(--muted);margin:10px 0 12px}.prompt-box{padding:14px;border-radius:15px;background:#f3f6f8;border:1px solid #e1e7eb;font-size:12.5px;line-height:1.6;color:#42515d;white-space:pre-wrap;max-height:200px;overflow:auto}.mission{background:linear-gradient(145deg,#13263a,#2e766f);color:#fff;border-radius:21px;padding:18px;margin-top:11px}.mission .kicker{color:#b9ddd8}.mission p{font-size:14px;line-height:1.65;margin:8px 0 0}nav{position:fixed;bottom:0;left:50%;transform:translateX(-50%);width:min(100%,430px);height:72px;background:rgba(255,255,255,.94);backdrop-filter:blur(14px);border-top:1px solid var(--line);display:flex;justify-content:space-around;align-items:center;z-index:20}.nav{width:25%;text-align:center;font-size:9.5px;font-weight:800;color:#87939d;cursor:pointer}.nav i{display:block;font-style:normal;font-size:17px;margin-bottom:2px}.nav.social{color:var(--navy)}