:root{--ink-950: #0D0A2E;--ink-900: #1B0E6B;--ink-800: #26168F;--primary: #2655F0;--primary-hover: #1b44d1;--primary-light: #EEF2FF;--paper-bg: #F4F3EF;--paper-card: #FFFFFF;--paper-border: #E8E4F4;--slate-border: #9B93D6;--slate-line: #CCC8E0;--text-main: #1A1A2E;--text-muted: #6B6B8A;--text-light: #9B99B5;--success: #15A86B;--success-bg: #F0FBF7;--success-border: #C3E8D8;--warning: #D97706;--warning-bg: #FFF9EC;--warning-border: #F5D9A8;--error: #DC2626;--error-bg: #FEF2F2;--error-border: #F5B8B8}*{box-sizing:border-box;margin:0;padding:0}html{scroll-behavior:smooth;width:100%;overflow-x:hidden}body{width:100%;overflow-x:hidden;font-family:Plus Jakarta Sans,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background-color:var(--paper-bg);color:var(--text-main);line-height:1.5;-webkit-font-smoothing:antialiased}.serif{font-family:Cormorant Garamond,Georgia,serif;font-style:italic}.serif-normal{font-family:Cormorant Garamond,Georgia,serif}.hw{font-family:Caveat,cursive}.container-custom{max-width:1240px;margin:0 auto;padding:0 5vw}.section-white{background:#fff}.section-paper{background:var(--paper-bg)}.section-dark{background:var(--ink-950);color:#fff}.notebook-paper-bg{background-color:#f8f7f3;background-image:linear-gradient(90deg,rgba(235,120,120,.2) 1px,transparent 1px),linear-gradient(0deg,rgba(155,147,214,.18) 1px,transparent 1px);background-size:100% 100%,100% 32px;background-position:70px 0,0 0}.slate{position:relative;border:1.5px dashed var(--slate-border);border-radius:16px;background:#fff;transition:box-shadow .2s ease,border-color .2s ease}.slate:hover{border-color:var(--primary)}.tab{position:absolute;top:-13px;left:50%;transform:translate(-50%);width:44px;height:13px;border-radius:7px;background:#fff;border:2.5px solid var(--ink-900);z-index:10}.tab-dark{position:absolute;top:-13px;left:50%;transform:translate(-50%);width:44px;height:13px;border-radius:7px;background:var(--ink-900);border:2.5px solid #6B8BFF;z-index:10}.slate-lined{background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='100%25' height='72'%3E%3Cline x1='0' y1='71' x2='100%25' y2='71' stroke='%23CCC8E0' stroke-width='1' stroke-dasharray='6 5'/%3E%3C/svg%3E");background-size:100% 72px;background-repeat:repeat-y;background-position:top left}.btnP{background:var(--primary);color:#fff;border:none;border-radius:10px;font-size:14px;font-weight:600;padding:11px 24px;cursor:pointer;transition:all .2s ease;display:inline-flex;align-items:center;justify-content:center;gap:8px;text-decoration:none;box-shadow:0 4px 14px #2655f040}.btnP:hover{background:var(--primary-hover);transform:translateY(-1px);box-shadow:0 6px 20px #2655f059}.btnS{background:#fff;color:var(--text-main);border:1.5px solid var(--paper-border);border-radius:10px;font-size:14px;font-weight:500;padding:11px 22px;cursor:pointer;transition:all .15s ease;display:inline-flex;align-items:center;justify-content:center;gap:8px;text-decoration:none}.btnS:hover{background:#f8f7fc;border-color:#d4d0e8;color:var(--primary)}.tag{display:inline-flex;align-items:center;gap:6px;font-size:11px;font-weight:600;padding:4px 12px;border-radius:20px}.chapter-label{font-size:11px;letter-spacing:.14em;text-transform:uppercase;color:var(--slate-border);font-weight:600;margin-bottom:12px}.card{background:#fff;border:1px solid var(--paper-border);border-radius:14px;padding:24px;box-shadow:0 2px 12px #1b0e6b08}.pencil-divider{display:flex;align-items:center;gap:16px;padding:24px 6vw}.pencil-divider hr{flex:1;border:none;border-top:1px dashed var(--slate-line)}.anim-el{opacity:0;transform:translateY(8px);transition:opacity .45s cubic-bezier(.16,1,.3,1),transform .45s cubic-bezier(.16,1,.3,1);width:100%}.anim-el.show{opacity:1;transform:translateY(0)}.katex{font-size:1.15em!important}.modal-overlay{position:fixed;top:0;right:0;bottom:0;left:0;background:#0d0a2ea6;-webkit-backdrop-filter:blur(6px);backdrop-filter:blur(6px);z-index:2000;display:flex;align-items:center;justify-content:center;padding:20px}.modal-content{background:#fff;border-radius:20px;max-width:860px;width:100%;max-height:90vh;overflow-y:auto;box-shadow:0 25px 50px -12px #00000040;border:1px solid var(--paper-border);position:relative}.grid-2{display:grid;grid-template-columns:1fr 1fr;gap:32px;align-items:center}.grid-3{display:grid;grid-template-columns:repeat(3,1fr);gap:20px}.grid-5{display:grid;grid-template-columns:repeat(5,1fr);gap:14px}@media(max-width:960px){.grid-2,.grid-3{grid-template-columns:1fr}.grid-5{grid-template-columns:1fr 1fr}}@media(max-width:600px){.grid-5{grid-template-columns:1fr}}