:root{--blue:#0088C8;--blue2:#0A9BD8;--blueSoft:#E8F7FD;--green:#68B828;--green2:#78C93A;--greenSoft:#EEF8E8;--ink:#202124;--text:#252A31;--muted:#65717D;--paper:#F7FAFB;--card:#FFFFFF;--line:#E4EEF2;--shadow:0 16px 42px rgba(0,136,200,.12)}
*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}html{scroll-behavior:smooth;background:var(--paper)}body{margin:0;min-height:100vh;min-height:100dvh;background:radial-gradient(circle at 14% 0%,rgba(104,184,40,.13),transparent 32%),radial-gradient(circle at 88% 8%,rgba(0,136,200,.13),transparent 34%),linear-gradient(180deg,#fff 0%,var(--paper) 100%);color:var(--text);font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;-webkit-font-smoothing:antialiased}button,input{font:inherit}button{cursor:pointer}button:disabled{cursor:not-allowed;opacity:.42}a{color:inherit;text-decoration:none}[hidden]{display:none!important}.page-shell{min-height:100vh;max-width:520px;margin:0 auto;padding:0 18px;display:flex;flex-direction:column}.site-header{height:78px;padding-top:env(safe-area-inset-top);display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);gap:12px}.brand{display:inline-flex;align-items:center;gap:10px;min-width:0}.brand-logo{width:156px;height:auto;display:block}.brand span{font-size:13px;color:var(--blue);font-weight:900;white-space:nowrap}.header-tag,.eyebrow{font-size:10px;letter-spacing:.18em;font-weight:900;color:var(--blue)}.header-tag{color:#8B98A3;white-space:nowrap}.header-actions{display:flex;align-items:center;gap:10px;flex:0 0 auto}.entry-link{display:inline-flex;align-items:center;justify-content:center;min-height:34px;padding:0 12px;border:1px solid rgba(0,136,200,.18);border-radius:999px;background:#fff;color:var(--blue);font-size:12px;font-weight:900;white-space:nowrap;box-shadow:0 6px 18px rgba(0,136,200,.06)}.entry-link:active{transform:scale(.98);background:var(--blueSoft)}main{flex:1}
.hero{position:relative;overflow:hidden;margin:24px 0 30px;padding:30px 24px 28px;border-radius:28px;background:linear-gradient(135deg,#fff 0%,#f7fcff 54%,#f2faed 100%);border:1px solid var(--line);box-shadow:var(--shadow)}.hero:before{content:"";position:absolute;left:0;top:0;right:0;height:8px;background:linear-gradient(90deg,var(--green),var(--blue))}.hero:after{content:"";position:absolute;right:-58px;top:-60px;width:158px;height:158px;border-radius:50%;background:linear-gradient(135deg,rgba(0,136,200,.13),rgba(104,184,40,.13));pointer-events:none}.hero-logo{position:relative;width:210px;height:auto;display:block;margin:2px 0 24px}.hero h1{position:relative;margin:13px 0 14px;font-size:42px;line-height:1.08;letter-spacing:-.06em;font-weight:950;color:var(--ink)}.hero h1 em{font-style:normal;color:var(--blue)}.hero p{position:relative;margin:0;font-size:14px;line-height:1.78;color:#536174}.hero-steps{position:relative;display:flex;gap:8px;flex-wrap:wrap;margin-top:24px}.hero-steps span{border:1px solid rgba(0,136,200,.16);background:#fff;border-radius:999px;padding:8px 12px;color:#304256;font-size:12px;box-shadow:0 6px 18px rgba(0,136,200,.06)}.hero-steps span:nth-child(2){border-color:rgba(104,184,40,.22)}
.section-heading{display:flex;justify-content:space-between;align-items:end;gap:16px;margin-bottom:14px}.section-heading h2{font-size:24px;letter-spacing:-.04em;margin:7px 0 0;color:var(--ink)}.text-button{background:none;border:0;color:var(--blue);font-size:13px;font-weight:800;padding:10px 0}.course-list{display:grid;grid-template-columns:1fr;gap:12px;margin-bottom:44px}.course-card,.loading-card,.empty-card{min-width:0;border:1px solid var(--line);background:var(--card);border-radius:22px}.course-card{appearance:none;text-align:left;color:var(--text);padding:22px;min-height:138px;display:flex;flex-direction:column;justify-content:space-between;box-shadow:0 12px 30px rgba(0,136,200,.08)}.course-card:active{transform:scale(.985);background:#f7fcff}.course-card-top{display:flex;justify-content:space-between;align-items:center;color:var(--green);font-size:11px;letter-spacing:.12em;font-weight:900}.course-card-top .arrow{font-size:20px;font-weight:500;color:var(--blue)}.course-card-title{font-size:21px;line-height:1.36;font-weight:850;letter-spacing:-.02em;overflow-wrap:anywhere;color:var(--ink)}.course-card-bottom{color:var(--muted);font-size:12px}.loading-card,.empty-card{grid-column:1/-1;padding:38px 24px;text-align:center;color:var(--muted);box-shadow:0 12px 30px rgba(0,136,200,.06)}.empty-icon{display:grid;place-items:center;width:60px;height:60px;margin:0 auto 18px;border-radius:20px;background:linear-gradient(135deg,var(--greenSoft),var(--blueSoft));color:var(--blue);font-size:28px}.empty-card h3{color:var(--ink);font-size:20px;margin:0 0 8px}.empty-card p{font-size:14px;line-height:1.75;margin:0}
.player-view{max-width:520px;margin:18px auto 54px}.back-button{display:inline-flex;align-items:center;gap:8px;background:none;border:0;color:#5F6E82;padding:9px 0;font-size:14px}.back-button span{font-size:22px}.lesson-heading{margin:22px 0 18px}.lesson-heading h1{font-size:30px;line-height:1.28;letter-spacing:-.04em;margin:8px 0 6px;overflow-wrap:anywhere;color:var(--ink)}.lesson-heading p{margin:0;color:var(--muted);font-size:13px}.player-card{border-radius:30px;padding:24px 18px;background:linear-gradient(150deg,var(--blue) 0%,#0478B1 62%,#05618E 100%);border:1px solid rgba(255,255,255,.28);box-shadow:0 20px 48px rgba(0,136,200,.24)}.card-topline{display:flex;justify-content:space-between;align-items:center;color:#e8f7fd;font-size:13px}.card-topline strong{font-size:13px;color:#BDF08C;letter-spacing:.08em}.waveform{height:112px;margin:22px 0 4px;display:flex;align-items:center;justify-content:center;gap:4px;overflow:hidden}.waveform span{display:block;flex:0 0 4px;border-radius:10px;background:linear-gradient(180deg,#BDF08C,var(--green));height:calc(15px + (var(--i,5) * 7px));opacity:.95;transform-origin:center}.waveform span:nth-child(5n+1){--i:3}.waveform span:nth-child(7n+2){--i:9}.waveform span:nth-child(3n+1){--i:6}.waveform span:nth-child(4n+3){--i:12}.waveform span:nth-child(9n){--i:4}.waveform.playing span{animation:pulse 750ms ease-in-out infinite alternate;animation-delay:calc(var(--i,5) * -75ms)}@keyframes pulse{to{transform:scaleY(.43);opacity:.55}}.listening-hint{text-align:center;color:#e6f6fc;font-size:13px;margin:8px 0 24px}.timeline{display:flex;align-items:center;gap:10px;color:#e8f7fd;font-size:12px;font-variant-numeric:tabular-nums}.timeline input{appearance:none;flex:1;min-width:0;height:6px;border-radius:999px;background:linear-gradient(to right,#BDF08C var(--progress,0%),rgba(255,255,255,.28) var(--progress,0%));outline:none}.timeline input::-webkit-slider-thumb{appearance:none;width:20px;height:20px;border-radius:50%;background:#fff;box-shadow:0 0 0 5px rgba(189,240,140,.2)}.timeline input::-moz-range-thumb{width:20px;height:20px;border:0;border-radius:50%;background:#fff}.transport{display:flex;align-items:center;justify-content:center;gap:28px;margin:27px 0}.circle-button{display:flex;align-items:center;justify-content:center;border:0;border-radius:50%}.side-button{width:50px;height:50px;color:#fff;background:rgba(255,255,255,.16);font-size:20px}.play-button{width:78px;height:78px;background:#fff;color:var(--blue);font-size:27px;box-shadow:0 12px 32px rgba(0,0,0,.18)}.play-options{display:flex;justify-content:center;gap:10px}.option-button{border:1px solid rgba(255,255,255,.22);border-radius:999px;background:rgba(255,255,255,.1);color:#fff;padding:10px 14px;font-size:12px;min-width:120px}.option-button strong{margin-left:7px;color:#BDF08C}.option-button.active{border-color:#BDF08C;background:rgba(104,184,40,.2)}
.speed-option-button{display:block;width:100%;margin-top:0}.practice-mode-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px;margin-top:10px}.practice-mode-grid .option-button{min-width:0;padding:10px 8px}.snowball-guide{min-height:38px;margin:10px 4px 0;color:#E8F7FD;font-size:11px;line-height:1.65;text-align:center}
.practice-card{margin-top:16px;border-radius:24px;padding:22px 20px;background:#fff;color:var(--text);box-shadow:0 12px 30px rgba(0,136,200,.08);border:1px solid var(--line)}.practice-card .eyebrow{color:var(--green)}.practice-card h2{font-size:21px;letter-spacing:-.03em;margin:7px 0 4px;color:var(--ink)}.practice-card p{color:#627187;line-height:1.65;font-size:13px;margin:0}.listen-only-card{position:relative;overflow:hidden}.listen-only-card:after{content:"";position:absolute;right:-34px;top:-46px;width:120px;height:120px;border-radius:50%;background:linear-gradient(135deg,rgba(0,136,200,.1),rgba(104,184,40,.14))}.player-footnote{font-size:12px;color:#7E8998;text-align:center;line-height:1.7;margin:18px 0}.site-footer{border-top:1px solid var(--line);padding:22px 0 calc(28px + env(safe-area-inset-bottom));display:flex;justify-content:space-between;gap:18px;color:#7E8998;font-size:12px}.site-footer a{color:var(--blue);font-weight:800}.toast{position:fixed;bottom:calc(24px + env(safe-area-inset-bottom));left:50%;transform:translate(-50%,15px);max-width:min(90vw,480px);padding:11px 18px;border-radius:12px;background:var(--blue);color:#fff;font-size:13px;font-weight:800;opacity:0;pointer-events:none;transition:opacity .2s,transform .2s;z-index:30;text-align:center}.toast.show{opacity:1;transform:translate(-50%,0)}
@media(min-width:701px){.page-shell{padding:0 24px}.course-list{grid-template-columns:repeat(2,minmax(0,1fr));max-width:960px}.player-view{max-width:690px}.hero{padding:42px 40px 38px}.hero h1{font-size:56px}.hero-logo{width:238px}}@media(max-width:380px){.brand-logo{width:132px}.header-tag{display:none}.hero{padding:27px 21px 25px}.hero-logo{width:178px}.hero h1{font-size:35px}.hero-steps span{font-size:11px;padding:8px 9px}.play-options{gap:6px}.option-button{min-width:0;flex:1;padding:10px 8px}.transport{gap:22px}}@media(prefers-reduced-motion:reduce){*,*:before,*:after{scroll-behavior:auto!important;animation-duration:.01ms!important;transition-duration:.01ms!important}}

/* Mobile hardening: WeChat, iOS Safari, narrow Android screens */
html{-webkit-text-size-adjust:100%;text-size-adjust:100%}body{overflow-x:hidden}.page-shell{width:100%;min-width:0}.course-card,.text-button,.back-button,.circle-button,.option-button{touch-action:manipulation}.course-card{min-height:132px}.timeline input{min-height:32px}.timeline input::-webkit-slider-thumb{width:24px;height:24px}.timeline input::-moz-range-thumb{width:24px;height:24px}.option-button,.text-button,.back-button{min-height:44px}.player-card,.hero,.practice-card{max-width:100%}.brand-logo,.hero-logo{max-width:100%;object-fit:contain}.course-card-title,.lesson-heading h1{word-break:break-word}@supports(height:100svh){.page-shell{min-height:100svh}}@media(max-width:430px){.page-shell{padding:0 14px}.site-header{height:70px}.brand-logo{width:140px}.brand span{font-size:12px}.header-tag{font-size:9px;letter-spacing:.12em}.entry-link{min-height:32px;padding:0 10px;font-size:11px}.hero{margin:18px 0 24px;padding:27px 20px 24px;border-radius:25px}.hero-logo{width:190px;margin-bottom:20px}.hero h1{font-size:37px}.hero p{font-size:13px}.section-heading h2{font-size:22px}.course-card{padding:20px;min-height:126px}.course-card-title{font-size:19px}.player-view{margin-top:12px}.lesson-heading{margin:14px 0 14px}.lesson-heading h1{font-size:25px}.player-card{border-radius:26px;padding:21px 15px}.waveform{height:94px;gap:3px}.waveform span{flex-basis:3px}.transport{gap:22px;margin:23px 0}.side-button{width:48px;height:48px}.play-button{width:74px;height:74px}.play-options{gap:8px}.option-button{min-width:0;flex:1;padding:10px 8px}.practice-card{padding:20px 17px}.site-footer{display:block}.site-footer span{display:block;margin-bottom:6px}}@media(max-width:360px){.page-shell{padding:0 10px}.site-header{height:64px}.brand-logo{width:120px}.brand span,.header-tag{display:none}.entry-link{min-height:30px;padding:0 9px;font-size:11px}.hero{padding:24px 16px 22px;border-radius:22px}.hero-logo{width:168px}.hero h1{font-size:31px}.hero-steps{gap:6px}.hero-steps span{font-size:10px;padding:7px 8px}.course-card{padding:17px}.course-card-title{font-size:18px}.lesson-heading h1{font-size:22px}.player-card{padding:18px 12px;border-radius:22px}.waveform{height:82px}.transport{gap:16px}.side-button{width:44px;height:44px}.play-button{width:68px;height:68px}.option-button{font-size:11px}.timeline{gap:7px}.timeline span{font-size:11px}}@media(orientation:landscape) and (max-height:520px){.hero{margin-top:14px;padding-top:22px}.hero h1{font-size:32px}.hero-logo{width:170px;margin-bottom:14px}.waveform{height:70px}.transport{margin:16px 0}.practice-card{display:none}}

.class-gate{margin:-10px 0 26px;padding:20px;border:1px solid var(--line);border-radius:24px;background:rgba(255,255,255,.86);box-shadow:0 12px 30px rgba(0,136,200,.07)}.class-gate-head{display:flex;align-items:flex-start;justify-content:space-between;gap:14px;margin-bottom:14px}.class-gate h2{margin:5px 0 0;font-size:22px;letter-spacing:-.04em;color:var(--ink)}.danger-text{color:#d35a4a}.class-picker{display:grid;gap:12px}.class-code-row{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}.class-code-row button{border:1px solid rgba(0,136,200,.18);border-radius:16px;background:#fff;color:#315368;font-weight:900;min-height:46px}.class-code-row button.active{background:linear-gradient(135deg,var(--blue),#07a0d7);border-color:var(--blue);color:#fff;box-shadow:0 10px 22px rgba(0,136,200,.18)}.class-number-label,.student-name-grid label{display:grid;gap:7px;font-size:12px;font-weight:850;color:#526172}.student-input{width:100%;border:1px solid var(--line);border-radius:15px;background:#fff;color:var(--ink);padding:13px 14px;outline:none;min-height:48px}.student-input:focus{border-color:var(--blue);box-shadow:0 0 0 4px rgba(0,136,200,.1)}.student-name-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px}.save-class{border:0;border-radius:16px;min-height:50px;background:linear-gradient(135deg,var(--green),var(--blue));color:#fff;font-weight:950;box-shadow:0 12px 28px rgba(0,136,200,.16)}.class-current{margin:6px 0 0;color:#304256;font-size:14px;font-weight:850;line-height:1.65}.class-note{margin:6px 0 0;color:#718091;font-size:12px;line-height:1.65}
@media(max-width:430px){.class-gate{padding:17px;border-radius:20px}.class-gate-head{align-items:center}.class-code-row{gap:7px}.student-name-grid{grid-template-columns:1fr}.class-gate h2{font-size:20px}}


/* Mobile quick navigation: lightweight, app-like, hidden on desktop */
.mobile-bottom-nav{display:none}
.password-dialog-open{overflow:hidden}.lesson-password-dialog{position:fixed;inset:0;z-index:90;display:flex;align-items:flex-end;justify-content:center;padding:18px max(14px,env(safe-area-inset-right)) calc(18px + env(safe-area-inset-bottom)) max(14px,env(safe-area-inset-left))}.lesson-password-dialog[hidden]{display:none}.lesson-password-backdrop{position:absolute;inset:0;width:100%;height:100%;border:0;border-radius:0;background:rgba(20,37,54,.46);backdrop-filter:blur(4px)}.lesson-password-sheet{position:relative;z-index:1;width:min(480px,100%);padding:24px;border:1px solid rgba(0,136,200,.16);border-radius:26px;background:#fff;box-shadow:0 24px 80px rgba(21,45,68,.28)}.password-sheet-head{display:flex;align-items:flex-start;justify-content:space-between;gap:16px}.password-sheet-head h2{margin:5px 0 0;font-size:24px;color:var(--ink)}.password-close{width:42px;height:42px;flex:none;border:0;border-radius:50%;background:#F1F7F9;color:#526171;font-size:27px;line-height:1}.password-course{margin:18px 0 15px;color:#526171;font-size:14px;font-weight:800;overflow-wrap:anywhere}.lesson-password-sheet label{display:block;margin-bottom:8px;color:#304256;font-size:13px;font-weight:900}.lesson-password-sheet input{display:block;width:100%;height:54px;padding:0 16px;border:1px solid #D5E5EB;border-radius:16px;background:#FBFDFF;color:var(--ink);font-size:16px;outline:none}.lesson-password-sheet input:focus{border-color:var(--blue);box-shadow:0 0 0 4px rgba(0,136,200,.11)}.password-error{min-height:22px;margin:8px 0;color:#A34C43;font-size:13px;font-weight:800}.password-submit{width:100%;min-height:54px;border:0;border-radius:16px;background:linear-gradient(135deg,var(--green),var(--blue));color:#fff;font-size:16px;font-weight:900;box-shadow:0 12px 28px rgba(0,136,200,.18)}
@media(max-width:820px){.page-shell{padding-bottom:calc(140px + env(safe-area-inset-bottom))}.course-list{scroll-margin-top:18px;scroll-margin-bottom:calc(130px + env(safe-area-inset-bottom))}.mobile-bottom-nav{position:fixed;left:50%;bottom:calc(10px + env(safe-area-inset-bottom));transform:translateX(-50%);z-index:45;width:min(360px,calc(100vw - 24px));display:grid;grid-template-columns:repeat(3,1fr);gap:6px;padding:8px;border:1px solid rgba(0,136,200,.16);border-radius:24px;background:rgba(255,255,255,.94);box-shadow:0 16px 40px rgba(0,136,200,.16);backdrop-filter:blur(14px)}.mobile-bottom-nav a{min-height:48px;border-radius:17px;display:flex;align-items:center;justify-content:center;flex-direction:column;gap:3px;color:#526171;font-size:11px;font-weight:900}.mobile-bottom-nav a:active{background:#f0faff;transform:scale(.98)}.mobile-bottom-nav span{font-size:15px;line-height:1;color:var(--blue)}.mobile-bottom-nav strong{font-size:11px;line-height:1}}
@media(max-width:360px){.mobile-bottom-nav{width:calc(100vw - 18px);padding:7px}.mobile-bottom-nav a{min-height:44px}.mobile-bottom-nav strong{font-size:10px}.practice-mode-grid{gap:5px}.practice-mode-grid .option-button{font-size:10px;padding:9px 4px}.practice-mode-grid .option-button strong{margin-left:3px}}

.class-code-row{margin-bottom:14px}.profile-actions{display:flex;gap:8px;margin-top:10px}.profile-actions button{min-height:44px;white-space:nowrap}.student-name-grid[hidden]{display:none}

.profile-login{margin-bottom:12px;min-height:44px}#profile-recovery{display:grid;gap:10px}#profile-recovery[hidden]{display:none}#profile-recovery .save-class{width:100%}
/* Compact sentence chooser: numbers only, shared with the current player state. */
.clip-picker{display:flex;gap:8px;max-width:100%;margin-top:16px;padding:2px 0 4px;overflow-x:auto;overscroll-behavior-x:contain;scrollbar-width:none;-webkit-overflow-scrolling:touch}.clip-picker::-webkit-scrollbar{display:none}.clip-choice{flex:0 0 40px;width:40px;height:40px;min-height:40px;margin:0;padding:0;border:1px solid rgba(255,255,255,.28);border-radius:50%;background:rgba(255,255,255,.1);color:#fff;font-size:13px;font-weight:800;line-height:38px;text-align:center;touch-action:manipulation}.clip-choice.active{border-color:#BDF08C;background:#fff;color:var(--blue);box-shadow:0 0 0 3px rgba(189,240,140,.2)}.clip-choice:focus-visible{outline:2px solid #BDF08C;outline-offset:2px}
/* Seven stages: keep the original four together and place BEC/BEC Pro/BTC evenly below. */
.class-code-row{grid-template-columns:repeat(12,minmax(0,1fr))}
.class-code-row button{grid-column:span 3;min-width:0}
.class-code-row button:nth-child(n+5){grid-column:span 4}