:root{--navy:#183e66;--teal:#087e8c;--gold:#f5c54b;--muted:#5b7085;--border:#dce6ef;--radius:18px}
body{background:#f5f8fc}a{color:var(--teal)}button,a,input,select,textarea{-webkit-tap-highlight-color:transparent}a:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible{outline:3px solid #e3a927;outline-offset:3px}
.site-header{padding:0;background:#fff;color:var(--navy);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:20;display:block}.header-inner{max-width:1120px;margin:auto;padding:17px 22px 11px;display:flex;justify-content:space-between;gap:16px;align-items:center}.brand{color:var(--navy);text-decoration:none;display:flex;align-items:center;gap:11px;font-size:1.18rem;font-weight:800}.brand-symbol{display:grid;place-items:center;width:38px;height:38px;background:var(--navy);color:#fff;border-radius:12px;font-size:23px}.site-header .brand-subtitle{font-size:.82rem;font-weight:500;color:var(--muted);display:block;margin-top:3px}.header-tag{color:var(--muted);font-size:.88rem}.site-nav{max-width:1120px;margin:auto;padding:0 22px;display:flex;gap:7px;overflow-x:auto;scrollbar-width:thin}.site-nav a{white-space:nowrap;padding:11px 16px 13px;border-bottom:3px solid transparent;text-decoration:none;font-weight:700;color:#53687d}.site-nav a[aria-current=page]{color:var(--teal);border-color:var(--teal)}.nav-count{background:#e8f4f3;border-radius:20px;font-size:.8rem;padding:1px 6px;margin-left:4px}.site-header .nav-count{display:inline}
.app-page{scroll-margin-top:130px}.app-page h1{font-size:1.85rem}.page-heading{margin-bottom:23px}.page-heading p{color:var(--muted);line-height:1.6;margin:9px 0 0}.eyebrow{color:var(--teal);font-size:.84rem;letter-spacing:.06em;font-weight:800;margin:0 0 10px}.home-hero{display:grid;grid-template-columns:1.3fr .7fr;gap:35px;align-items:center;padding:35px;border-radius:24px;background:#e9f3f7;margin-bottom:24px;overflow:hidden}.home-hero h1{font-size:2.3rem;line-height:1.25;margin:0 0 13px}.home-hero p{line-height:1.7;color:#49647b;margin:0 0 20px}.hero-art svg{width:100%;display:block;max-height:245px}.primary-button,.secondary-button{display:inline-flex;align-items:center;justify-content:center;border-radius:11px;padding:12px 18px;font-weight:750;text-decoration:none;border:1px solid transparent;gap:8px;cursor:pointer;font:inherit}.primary-button{background:var(--navy);color:#fff}.primary-button:hover{background:#235980}.secondary-button{background:white;color:var(--navy);border-color:#bccede}.button-row{display:flex;flex-wrap:wrap;gap:10px}.home-features{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:17px;margin-bottom:31px}.feature-card{display:block;padding:24px;border:1px solid var(--border);border-radius:var(--radius);background:white;text-decoration:none;color:var(--navy)}.feature-card:hover{border-color:#7cb3bc;box-shadow:0 8px 24px #183e660b}.feature-number{display:inline-grid;place-items:center;width:35px;height:35px;border-radius:10px;background:#e5f3f2;color:var(--teal);font-weight:800;margin-bottom:16px}.feature-card h2{margin:0 0 8px;font-size:1.16rem}.feature-card p{color:var(--muted);line-height:1.6;font-size:.96rem;margin:0 0 17px}.feature-card b{font-size:.9rem;color:var(--teal)}.section-heading{display:flex;align-items:center;justify-content:space-between;gap:12px;margin:0 0 16px}.section-heading h2{margin:0;font-size:1.28rem}.section-heading a{font-size:.93rem;text-decoration:none;font-weight:700}.chapter-label{font-weight:700;font-size:.9rem;color:var(--muted);margin:0 0 14px}.topic-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.topic-card{border:1px solid var(--border);border-radius:var(--radius);background:#fff;padding:20px;text-align:left;color:var(--navy);display:flex;flex-direction:column;width:100%;font:inherit}.topic-card:hover{border-color:#7cb3bc}.topic-card h3{font-size:1.09rem;margin:14px 0 8px}.topic-card p{color:var(--muted);line-height:1.5;margin:0 0 17px;font-size:.92rem;flex:1}.topic-card .topic-icon{height:90px;width:100%;background:#f4f9fc;border-radius:11px;display:flex;align-items:center;justify-content:center;overflow:hidden}.topic-icon svg{height:94px;width:146px}.topic-card .topic-open{font-size:.88rem;color:var(--teal);font-weight:700}.home-footer-note{margin:22px 0 0;color:var(--muted);font-size:.88rem}.back-link{display:inline-block;border:0;background:none;color:var(--teal);padding:0;margin-bottom:15px;font-size:.95rem;cursor:pointer}.notes-grid{display:grid;grid-template-columns:1.15fr .85fr;gap:20px}.note-card{padding:25px}.note-card h2{font-size:1.2rem}.note-definition{font-size:1.16rem;line-height:1.7;margin:12px 0 20px}.simple-facts{padding-left:23px;line-height:1.8;margin:13px 0 0}.worked-example{margin-top:20px;padding:19px;background:#edf7f4;border-radius:12px}.worked-example h3{font-size:1rem;margin:0 0 8px}.worked-example p{line-height:1.7;margin:0}.mistake-note{border-left:4px solid #efbf43;margin-top:19px;padding:13px 15px;background:#fff9e7;line-height:1.65;font-size:.97rem}.notes-diagram{max-width:none;margin:15px 0;background:#f7fbff}.topic-tabs{margin:20px 0}.topic-tabs .tab{padding:9px 15px;font-size:.93rem}.topic-tabs #tab-practice{display:none}.app-page-explore .quiz{display:none}.explore-footer{margin-top:22px;display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap}.practice-head p{max-width:540px}.practice-head h1{font-size:1.6rem}.practice-status{background:#edf5f8}.wrong-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.wrong-card{padding:22px}.wrong-card h3{font-size:1.06rem;line-height:1.6;margin:10px 0 15px}.wrong-card .practice-diagram{max-width:330px;margin:0 auto 17px}.empty-state{padding:44px 25px;text-align:center;background:#fff;border:1px dashed #b7cbd9;border-radius:20px}.empty-state h2{margin:10px 0}.empty-state p{color:var(--muted);line-height:1.7}.empty-symbol{font-size:32px;color:var(--teal)}
.site-footer{max-width:1120px;margin:auto;padding:20px 22px 35px;border-top:1px solid var(--border);display:flex;justify-content:space-between;gap:14px;color:var(--muted);font-size:.86rem}.footer-report{border:0;background:none;color:var(--teal);font:inherit;font-weight:700;padding:0;cursor:pointer}.report-fab{position:fixed;right:22px;bottom:22px;z-index:30;border:1px solid #aecbd3;background:#fff;color:var(--navy);box-shadow:0 4px 20px #183e661a;padding:11px 16px;border-radius:99px;font-weight:700;font-size:.91rem}.report-fab:hover{background:#edf7f7}.report-dialog{border:0;border-radius:20px;max-width:520px;width:calc(100% - 28px);padding:26px;box-shadow:0 16px 80px #183e6633;color:#19324d;max-height:90dvh;overflow:auto}.report-dialog::backdrop{background:#16375466}.dialog-heading{display:flex;justify-content:space-between;align-items:center;gap:15px;margin-bottom:12px}.dialog-heading h2{margin:0}.close-dialog{border:0;background:#edf3f8;border-radius:99px;height:32px;width:32px;color:var(--navy);font-size:22px;padding:0}.report-dialog p{line-height:1.6;color:var(--muted);font-size:.92rem}.report-context{padding:11px 13px;border-radius:10px;background:#edf5f8;font-size:.9rem;line-height:1.6;max-height:145px;overflow:auto}.report-form label{display:block;margin:16px 0 7px;font-weight:700}.report-form select,.report-form textarea{width:100%;font:inherit;color:#19324d;background:#fff;border:1px solid #aebfce;border-radius:10px;padding:11px}.report-form textarea{min-height:135px;resize:vertical;line-height:1.6}.report-character-count{text-align:right;font-size:.8rem;color:var(--muted);margin:5px 0}.report-status{min-height:22px;line-height:1.6;font-size:.93rem;margin:12px 0}.report-status.error{color:#a44433}.report-status.success{color:#087353}.report-honey{position:absolute;left:-9999px;height:1px;width:1px;overflow:hidden}.report-submit{width:100%;margin-top:3px}.report-submit:disabled{opacity:.55;cursor:default}.report-copy{width:100%;margin-top:10px}.report-privacy{font-size:.8rem!important;margin-bottom:0!important}.app-ready #legacy-intro{display:none}
@media(max-width:820px){.home-hero{padding:25px;gap:20px}.home-hero h1{font-size:1.9rem}.home-features{gap:12px}.feature-card{padding:20px}.topic-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.notes-grid{grid-template-columns:1fr}.notes-grid .note-card:last-child{order:-1}.notes-diagram{max-width:380px;margin:12px auto}.wrong-grid{grid-template-columns:1fr}}@media(max-width:580px){.header-inner{padding:13px 16px 7px}.header-tag{display:none}.brand{font-size:1.02rem}.brand-symbol{height:33px;width:33px}.site-header .brand-subtitle{font-size:.75rem}.site-nav{padding:0 10px;gap:0}.site-nav a{padding:10px 12px 11px;font-size:.89rem}.home-hero{grid-template-columns:1fr;padding:23px;margin-bottom:18px}.hero-art{display:none}.home-hero h1{font-size:1.9rem}.home-features{grid-template-columns:1fr;gap:11px}.feature-card{padding:19px;display:grid;grid-template-columns:38px 1fr;column-gap:15px}.feature-number{grid-row:1/4;margin:0}.feature-card h2{margin-bottom:7px}.feature-card p{margin-bottom:8px}.topic-grid{gap:11px}.topic-card{padding:14px}.topic-card h3{font-size:1rem}.topic-card p{font-size:.88rem}.topic-icon{height:70px!important}.topic-card .topic-icon svg{height:75px;width:112px}.app-page h1{font-size:1.6rem}.note-card{padding:19px}.report-fab{right:13px;bottom:13px;padding:10px 14px;font-size:.86rem}.site-footer{padding-bottom:78px;flex-direction:column}.report-dialog{padding:21px}.home-footer-note{font-size:.85rem}}
.site-header .brand>span:last-child{display:block;color:var(--navy);font-size:inherit}.site-header .brand-symbol{display:grid;color:#fff}.site-header .nav-count{color:var(--teal)}
.report-form input[type=file]{display:block;width:100%;padding:10px;border:1px solid #aebfce;border-radius:10px;background:#fff;font:inherit;font-size:.9rem}.report-dialog .screenshot-hint{font-size:.82rem;margin:0 0 10px}#screenshot-status{font-size:.84rem;line-height:1.6;margin:7px 0;color:var(--muted)}#screenshot-preview img{display:block;max-width:100%;max-height:180px;border:1px solid var(--border);border-radius:9px;margin:10px auto}#screenshot-remove{margin:0}