/* Unified lesson page shell — shared across RU / EN / 中文. */
.lesson{width:min(920px,calc(100% - 40px));margin:0 auto;padding:0 0 5rem;color:var(--text,#e8eef9);line-height:1.8}
.lesson-standard-hero{margin:0 0 1.5rem;padding:2.2rem 0 0}
.lesson-standard-hero .eyebrow{margin:0 0 .8rem}
.lesson-standard-hero h1{max-width:900px;margin:.25rem 0 1rem;font-size:clamp(2rem,4vw,3.15rem);line-height:1.12;letter-spacing:-.035em}
.lesson-standard-hero .lead{max-width:78ch;margin:0;color:var(--muted,#aab7cc);font-size:clamp(1rem,1.5vw,1.15rem);line-height:1.75}
.lesson-standard-hero .outcomes,.lesson-standard-hero .panel{margin:1.35rem 0 0}
.lesson-standard-article{max-width:100%;min-width:0}
.lesson-standard-article>section,.lesson-standard-article>div{min-width:0}
.lesson-standard-article h2{margin:2.5rem 0 .8rem;line-height:1.25}
.lesson-standard-article h3{margin:1.7rem 0 .65rem;line-height:1.3}
.lesson-standard-article p,.lesson-standard-article li{line-height:1.8}
.lesson-standard-article img,.lesson-standard-article svg,.lesson-standard-article video{max-width:100%;height:auto}
.lesson-standard-article table{max-width:100%;display:block;overflow-x:auto}
.lesson-standard-article pre{max-width:100%;overflow-x:auto}
.lesson-planet-banner{position:relative;display:grid;grid-template-columns:minmax(0,1fr) 160px;gap:22px;align-items:center;margin:1.5rem 0 0;padding:20px 24px;border:1px solid rgba(120,160,230,.24);border-radius:18px;background:radial-gradient(circle at 82% 50%,rgba(100,140,240,.18),transparent 24%),linear-gradient(120deg,rgba(20,37,65,.82),rgba(15,24,44,.74));overflow:hidden}
.lesson-planet-banner .planet-label{display:block;font-size:10px;letter-spacing:.16em;color:var(--blue,#83baff);font-weight:800}
.lesson-planet-banner p{margin:8px 0 0;color:var(--muted,#aab7cc);font-size:13px;line-height:1.65}
.lesson-planet-art{position:relative;width:140px;height:115px;margin:auto;display:grid;place-items:center}
.lesson-planet-art:before,.lesson-planet-art:after{content:"";position:absolute;width:136px;height:52px;border:1px solid rgba(111,166,255,.42);border-radius:50%;transform:rotate(-24deg)}
.lesson-planet-art:after{width:112px;height:39px;transform:rotate(34deg);border-color:rgba(174,135,255,.38)}
.lesson-planet-sphere{position:relative;z-index:1;width:74px;height:74px;border-radius:50%;display:grid;place-items:center;background:radial-gradient(circle at 30% 25%,#e3eaff 0,#9bb9ee 15%,#5279c1 44%,#263c78 76%,#101b3a 100%);border:1px solid rgba(218,232,255,.72);box-shadow:0 0 28px rgba(93,143,230,.52),inset -12px -10px 20px rgba(4,10,29,.5);font:800 12px Manrope,Arial,sans-serif;color:#f5f8ff;letter-spacing:.04em}
.lesson-standard-article .quiz,.lesson-standard-article .interactive-quiz-item{margin:14px 0;padding:16px 18px;border:1px solid var(--lds-line,rgba(120,160,230,.3));border-radius:14px;background:var(--lds-surface,rgba(20,35,58,.55));color:var(--lds-ink,inherit)}
.lesson-standard-article .quiz h3,.lesson-standard-article .interactive-quiz-item h3{margin:0 0 .65rem}
.lesson-standard-article .quiz details{margin-top:10px}
.lesson-standard-article .quiz summary{cursor:pointer;font-weight:700;color:var(--lds-accent,#79b5ff)}
.lesson-standard-article .quiz-options,.lesson-standard-article .lesson-check-options{display:grid;gap:9px;margin:12px 0}
.lesson-standard-article .quiz-option,.lesson-standard-article .lesson-check-option{display:flex;gap:10px;align-items:flex-start;line-height:1.55;cursor:pointer}
.lesson-standard-article .quiz-check-button{border:0;border-radius:9px;padding:10px 16px;background:var(--lds-accent,#246bd6);color:#fff;font:700 14px inherit;cursor:pointer}
@media(max-width:700px){.lesson{width:min(calc(100% - 32px),920px)}.lesson-standard-hero{padding-top:1.3rem}.lesson-planet-banner{grid-template-columns:1fr;padding:16px}.lesson-planet-art{height:95px}.lesson-standard-article table{font-size:.9rem}}
@media(max-width:420px){.lesson{width:calc(100% - 24px)}.lesson-standard-hero h1{font-size:1.9rem}.lesson-standard-article .quiz,.lesson-standard-article .interactive-quiz-item{padding:13px}}