:root{font-family:-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:#203b35;background:#f7f6f2;color-scheme:light}*{box-sizing:border-box}body{margin:0;padding-bottom:calc(85px + env(safe-area-inset-bottom))}header{position:sticky;top:0;background:#f7f6f2;z-index:5;padding:calc(15px + env(safe-area-inset-top)) 18px 15px;display:flex;justify-content:space-between;border-bottom:1px solid #dce5df}header span,small{font-size:12px;color:#567069}main{max-width:850px;margin:auto;padding:18px}h1{font-size:25px}h2{font-size:19px}h3{font-size:16px}p{line-height:1.7;white-space:pre-wrap;overflow-wrap:anywhere}button,a.button{font:inherit;border:1px solid #ccdad2;background:white;color:#203b35;border-radius:10px;padding:12px;min-height:44px;cursor:pointer;text-decoration:none}button.primary{background:#3d7771;color:white;border:0}button:disabled{opacity:.5}input,textarea,select{font:inherit;font-size:16px;border:1px solid #c6d5cc;padding:12px;border-radius:8px;width:100%;margin:6px 0;background:white;color:#203b35}textarea{min-height:100px}article,.card,details{background:white;border:1px solid #dce5df;border-radius:12px;padding:15px;margin:12px 0}summary{cursor:pointer;min-height:32px;line-height:1.6}.grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(125px,1fr));gap:10px}.row{display:flex;flex-wrap:wrap;gap:8px;margin:10px 0}.row>*{flex:1}.muted{color:#567069;font-size:13px}.good{color:#207b4d}.bad{color:#a64136}audio{width:100%;margin:8px 0}.player{position:sticky;top:60px;background:#f7f6f2;z-index:3;padding:8px;border-bottom:1px solid #dce5df}nav{position:fixed;bottom:0;left:0;right:0;display:flex;background:#fff;border-top:1px solid #dce5df;padding:8px 4px calc(8px + env(safe-area-inset-bottom));z-index:10}nav button{flex:1;border:0;padding:8px 2px;font-size:12px;border-radius:6px}nav button.active{background:#e4eee9;color:#23665d}#notice{position:fixed;top:65px;left:10%;right:10%;z-index:20;background:#203b35;color:white;padding:12px;border-radius:9px;display:none}table{width:100%;border-collapse:collapse;font-size:13px}td{border:1px solid #dce5df;padding:6px}progress{width:100%;accent-color:#3d7771}.sticky{position:sticky;top:65px;background:#f7f6f2;padding:8px;z-index:2}
/* A gentle notebook theme: readable lessons, playful navigation, no external assets. */
:root{--ink:#304d47;--muted:#71847b;--mint:#d9eee2;--cream:#fffaf0;--peach:#ffe2d1;--rose:#f9dde5;--line:#e8e8db;color:var(--ink);background:var(--cream)}
body{background:radial-gradient(circle at 12% 10%,#fce8dd 0,transparent 32%),radial-gradient(circle at 95% 38%,#e0f0e3 0,transparent 36%),#fffaf0;background-attachment:fixed}
header{background:#fffaf0ee;border-bottom:1px solid #e9e8d9;backdrop-filter:blur(14px);padding-bottom:14px}header b{display:flex;align-items:center;gap:9px;font-weight:750;letter-spacing:.1px}header b:before{content:'🌱';display:grid;place-items:center;width:34px;height:34px;background:#e0efdf;border-radius:13px 13px 13px 5px}header span{font-size:11px;align-self:center;color:#758579}
main{padding:20px 18px 28px}h1{font-size:25px;line-height:1.45;letter-spacing:-.5px;margin:10px 0 20px}h1:after{content:'';display:block;width:38px;height:5px;margin-top:9px;border-radius:20px;background:#e9bd92}
h2,h3{line-height:1.5}article,.card,details{border:1px solid var(--line);border-radius:21px;background:#fffefa;box-shadow:0 4px 0 #e9e7d844,0 8px 24px #5b735206;padding:17px;margin:13px 0}details[open]{border-color:#c9ddce;background:#fffefb}summary{list-style:none;position:relative;padding:2px 28px 2px 0;font-weight:650;line-height:1.7}summary::-webkit-details-marker{display:none}summary:after{content:'+';position:absolute;right:0;top:0;background:#edf3e9;color:#65886c;width:25px;height:25px;border-radius:9px;text-align:center;font-size:18px;font-weight:400}details[open]>summary:after{content:'−'}
button,a.button{border:1px solid #dbe5d7;border-radius:15px;background:#fffefa;box-shadow:0 3px 0 #e0e6d8;color:var(--ink);line-height:1.45;transition:transform .12s,background .12s}button:active,a.button:active{transform:translateY(2px);box-shadow:0 1px 0 #e0e6d8}button.primary{background:#537f6b;color:#fffefa;border:1px solid #537f6b;box-shadow:0 3px 0 #3c6452}button:focus-visible,input:focus-visible,textarea:focus-visible,summary:focus-visible{outline:3px solid #c1dbc7;outline-offset:3px}
input,textarea,select{border:1px solid #dce4d7;border-radius:14px;background:#fffefa;color:var(--ink);box-shadow:inset 0 2px 4px #61734b04}input::placeholder,textarea::placeholder{color:#91a08e}textarea{line-height:1.7}p{line-height:1.8}.muted,small{color:var(--muted)}.grid{grid-template-columns:repeat(auto-fit,minmax(145px,1fr));gap:12px}.grid>button{padding:16px 12px;min-height:85px;text-align:left;background:#fffefa}.grid>button:nth-child(4n+2){background:#f1f5e8}.grid>button:nth-child(4n+3){background:#fff0e6}.grid>button:nth-child(4n){background:#fcf0f0}
.player{border:1px solid #d4e2d4;border-radius:18px;background:#edf5e9f2;padding:12px;margin:15px 0;backdrop-filter:blur(12px)}.player b{font-size:13px}audio{height:44px}.good{color:#4b825e}.bad{color:#ba6e5d}#notice{background:#426d59;border:1px solid #eef4e8;border-radius:17px;box-shadow:0 6px 22px #36503e20;font-size:14px}
nav{background:#fffdf6f5;border-color:#e6e7d8;border-radius:22px 22px 0 0;box-shadow:0 -5px 22px #5b735208;backdrop-filter:blur(18px);gap:2px}nav button{box-shadow:none;min-height:52px;border-radius:15px;background:transparent;font-size:11px;color:#80907c}nav button:before{display:block;font-size:18px;line-height:1.3;margin-bottom:3px}nav button[data-nav=home]:before{content:'⌂'}nav button[data-nav=core]:before{content:'▤'}nav button[data-nav=listening]:before{content:'♫'}nav button[data-nav=vocab]:before{content:'Aa';font-size:16px;font-weight:700}nav button[data-nav=review]:before{content:'↻'}nav button[data-nav=more]:before{content:'⋯'}nav button.active{background:#e6efdd;color:#477457;box-shadow:none;font-weight:700}
@media(prefers-reduced-motion:reduce){button,a.button{transition:none}}@media(max-width:380px){main{padding:16px 12px}header{padding-left:12px;padding-right:12px}header span{max-width:125px;text-align:right}.grid{grid-template-columns:1fr 1fr}}
/* Neutral blue, white, gray and black reading palette. Rounded cards stay; decorative color washes go. */
:root{--control-line:#7f8b9d;--page:#f1f3f6;--surface:#ffffff;--field:#f5f7fa;--ink:#1b2432;--muted:#526174;--line:#d4dae3;--accent:#245ca6;--accent-soft:#e4edfb;--primary:#245ca6;--primary-ink:#ffffff;--good:#267244;--bad:#a13b3b;--warning:#986400;color-scheme:light;background:var(--page);color:var(--ink)}
:root[data-theme=dark]{--control-line:#7d899c;--page:#171b22;--surface:#232a35;--field:#1c232d;--ink:#e6ebf3;--muted:#b2bdce;--line:#414c5d;--accent:#9bc2ff;--accent-soft:#2c3e59;--primary:#9bc2ff;--primary-ink:#142643;--good:#83c99d;--bad:#efa9a9;--warning:#e6c16c;color-scheme:dark}
body{background:var(--page);color:var(--ink)}header{background:var(--page);border-color:var(--line);backdrop-filter:none;gap:10px;align-items:center;flex-wrap:wrap}header b:before{content:'▤';color:var(--accent);background:var(--accent-soft);font-size:22px}header span{color:var(--muted);margin-left:auto;max-width:none}#theme-toggle{font-size:12px;padding:8px 11px;min-height:40px;box-shadow:none;white-space:nowrap}h1:after{background:var(--line)}article,.card,details{background:var(--surface);border-color:var(--line);box-shadow:0 3px 0 #00000008}details[open]{background:var(--surface);border-color:var(--accent)}summary:after{background:var(--accent-soft);color:var(--accent)}button,a.button{background:var(--surface);border-color:var(--line);color:var(--ink);box-shadow:0 2px 0 #0000000a}button.primary{background:var(--primary);color:var(--primary-ink);border-color:var(--primary);box-shadow:none}button:focus-visible,input:focus-visible,textarea:focus-visible,summary:focus-visible{outline-color:var(--accent)}input,textarea,select{background:var(--field);color:var(--ink);border-color:var(--line)}input::placeholder,textarea::placeholder{color:var(--muted)}.muted,small{color:var(--muted)}.grid>button,.grid>button:nth-child(4n+2),.grid>button:nth-child(4n+3),.grid>button:nth-child(4n){background:var(--surface)}.player,.sticky{background:var(--page);border-color:var(--line);backdrop-filter:none}.player{top:calc(78px + env(safe-area-inset-top))}.good{color:var(--good)}.bad{color:var(--bad)}td{border-color:var(--line)}progress{accent-color:var(--accent)}nav{background:var(--page);border-color:var(--line);backdrop-filter:none;box-shadow:0 -3px 18px #00000008}nav button{background:transparent;color:var(--muted);box-shadow:none}nav button.active{background:var(--accent-soft);color:var(--accent)}#notice{background:var(--primary);color:var(--primary-ink);border-color:var(--line)}
@media(max-width:420px){header span{display:none}header{flex-wrap:nowrap}#theme-toggle{margin-left:auto}.player{top:calc(65px + env(safe-area-inset-top))}}
.choice-exercise fieldset{padding:0;border:0;min-width:0;display:grid;gap:9px;margin:12px 0 16px}.choice{display:flex;align-items:flex-start;gap:10px;padding:13px 12px;border:1px solid var(--line);border-radius:15px;background:var(--field);cursor:pointer;min-height:48px;line-height:1.65}.choice input{width:18px;height:18px;flex:0 0 18px;margin:4px 0 0;accent-color:var(--accent);box-shadow:none}.choice:has(input:checked){background:var(--accent-soft);border-color:var(--accent)}.choice:has(input:focus-visible){outline:2px solid var(--accent);outline-offset:2px}.choice span{overflow-wrap:anywhere}.sr-only{position:absolute;width:1px;height:1px;padding:0;overflow:hidden;clip-path:inset(50%);white-space:nowrap}

input,textarea,select,.choice{border-color:var(--control-line)}button:not(.primary):not(nav button){border-color:var(--control-line)}

#install-status{border-left:3px solid var(--warning);padding-left:12px;color:var(--muted)}