:root{--color-bg: #f5f5f7;--color-surface: #ffffff;--color-surface-hover: #f0f0f2;--color-border: #e0e0e0;--color-primary: #6366f1;--color-primary-hover: #4f46e5;--color-accent: #0ea5e9;--color-text: #1a1a1a;--color-text-muted: #6b7280;--font-sans: "Outfit", system-ui, sans-serif;--font-mono: "JetBrains Mono", monospace;--bp-md: 768px;--bp-lg: 1024px;--safe-bottom: env(safe-area-inset-bottom, 0px);--bottom-nav-h: 56px}*{box-sizing:border-box}body{margin:0;font-family:var(--font-sans);background:var(--color-bg);color:var(--color-text);line-height:1.6;-webkit-font-smoothing:antialiased}input,select,textarea{font-size:16px}#root{min-height:100vh;min-height:100dvh}.bottom-nav{display:none}@media (max-width: 767px){.bottom-nav{position:fixed;bottom:0;left:0;right:0;display:flex;align-items:stretch;height:calc(var(--bottom-nav-h) + var(--safe-bottom));padding-bottom:var(--safe-bottom);background:var(--color-surface);border-top:1px solid var(--color-border);z-index:50}.bottom-nav a{position:relative;flex:1;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:2px;text-decoration:none;color:var(--color-text-muted);font-size:.65rem;font-weight:500;min-height:44px;-webkit-tap-highlight-color:transparent}.bottom-nav a.active{color:var(--color-primary);font-weight:700}.bottom-nav .tab-icon{font-size:1.25rem;line-height:1}}.account-backdrop{display:none}@media (max-width: 767px){.account-backdrop{display:block;position:fixed;top:0;right:0;bottom:0;left:0;background:#0006;z-index:60}.account-sheet{position:fixed;bottom:0;left:0;right:0;background:var(--color-surface);border-radius:16px 16px 0 0;padding:1.25rem 1.25rem calc(1.25rem + var(--safe-bottom));z-index:61;max-height:85vh;overflow:auto;animation:sheet-up .22s ease-out}@keyframes sheet-up{0%{transform:translateY(100%)}to{transform:translateY(0)}}}.course-toc-backdrop{display:none}@media (max-width: 767px){.course-toc-backdrop{display:block;position:fixed;top:0;right:0;bottom:0;left:0;background:#0006;z-index:55}.course-toc-sheet{position:fixed;bottom:0;left:0;right:0;background:var(--color-surface);border-radius:16px 16px 0 0;padding:1.25rem 1.25rem calc(1.25rem + var(--safe-bottom));z-index:56;max-height:80vh;overflow:auto;animation:sheet-up .22s ease-out}}@media (max-width: 767px){.desktop-sidebar{display:none!important}}button{font-family:inherit;cursor:pointer}a{color:var(--color-primary);text-decoration:none}a:hover{text-decoration:underline}.toast-viewport{position:fixed;top:16px;left:50%;transform:translate(-50%);z-index:2000;display:flex;flex-direction:column;gap:8px;align-items:center;pointer-events:none}@media (max-width: 767px){.toast-viewport{left:12px;right:12px;transform:none;width:auto}.toast-item{max-width:100%!important;min-width:0!important}}.toast-item{transform-origin:top center;will-change:transform,opacity}@keyframes toast-in{0%{opacity:0;transform:translateY(-10px) scale(.98)}to{opacity:1;transform:translateY(0) scale(1)}}@keyframes toast-out{0%{opacity:1;transform:translateY(0) scale(1)}to{opacity:0;transform:translateY(-8px) scale(.98)}}