/* VTI Lessons — giao diện theo hệ Nocturne (nền tối, Inter, accent viền) */
.vti, .vti-scope {
	--vti-bg: #161826; --vti-surface: #232532; --vti-text: #e9e9ed; --vti-accent: #9184d9;
	--vti-accent-300: #d2cefd; --vti-accent-400: #b5abfc; --vti-accent-800: #423a6a; --vti-accent-100: #f5f4ff;
	--vti-n300: #cfd3e5; --vti-n500: #9397ab; --vti-n600: #75798c; --vti-n700: #595d6c; --vti-n800: #3f424d; --vti-n900: #292b31;
	--vti-divider: color-mix(in srgb, #e9e9ed 16%, transparent);
	--vti-shadow-sm: 0 0 0 1px #3f424d; --vti-shadow-md: 0 0 0 1px #595d6c, 0 6px 18px rgba(0,0,0,.55); --vti-shadow-lg: 0 0 0 1px #9397ab, 0 16px 40px rgba(0,0,0,.65);
	--vti-r: 8px; --vti-r-lg: 14px;
	font-family: "Inter", system-ui, sans-serif; color: var(--vti-text); font-size: 15px; line-height: 1.55;
}
body.vti { margin: 0 !important; background: radial-gradient(1200px 600px at 10% -10%, #20233a 0%, #161826 60%) fixed, #161826 !important; color: var(--vti-text) !important; min-height: 100vh; }
.vti-scope { background: var(--vti-bg); padding: 22px; border-radius: var(--vti-r-lg); }
.vti *, .vti-scope * { box-sizing: border-box; }
.vti h1, .vti h2, .vti h3, .vti h6, .vti-scope h6 { font-family: inherit; font-weight: 500; letter-spacing: -.015em; line-height: 1.12; margin: 0 0 6px; color: var(--vti-text); }
.vti h1 { font-size: 46px; } .vti h2 { font-size: 32px; }
.vti a { color: var(--vti-accent); text-underline-offset: 3px; }
.vti a:hover { color: var(--vti-accent-400); }
.vti :focus-visible, .vti-scope :focus-visible { outline: 2px solid var(--vti-accent); outline-offset: 2px; }
.vti ::selection { background: color-mix(in srgb, var(--vti-accent) 30%, transparent); }
.vti-muted { color: color-mix(in srgb, var(--vti-text) 58%, transparent); }
.vti-kicker { font-size: 10px; letter-spacing: .1em; text-transform: uppercase; color: var(--vti-accent); }
.vti-label { font-size: 12px !important; letter-spacing: .08em; text-transform: uppercase; color: var(--vti-n500) !important; margin: 0 0 8px !important; }

/* Nút */
.vti-btn { display: inline-flex; align-items: center; justify-content: center; gap: 6px; cursor: pointer; text-decoration: none !important; font: 500 14px/1.2 "Inter", system-ui, sans-serif; color: var(--vti-text) !important; background: transparent; border: 1px solid var(--vti-divider); padding: 7px 12px; border-radius: var(--vti-r); white-space: nowrap; }
.vti-btn:hover { background: color-mix(in srgb, var(--vti-text) 7%, transparent); }
.vti-btn:active { background: color-mix(in srgb, var(--vti-text) 14%, transparent); }
.vti-btn-primary { color: var(--vti-accent) !important; border-color: var(--vti-accent); }
.vti-btn-primary:hover { background: color-mix(in srgb, var(--vti-accent) 12%, transparent); }
.vti-btn-primary:active { background: color-mix(in srgb, var(--vti-accent) 22%, transparent); }
.vti-icon { width: 34px; height: 34px; padding: 0; }
.vti-btn.is-disabled { opacity: .35; pointer-events: none; }
.vti-tag { display: inline-flex; align-items: center; font-size: 11px; padding: 3px 10px; border-radius: 6px; background: var(--vti-n800); color: var(--vti-n300); white-space: nowrap; }

/* Header */
.vti-nav { max-width: 1240px; margin: 0 auto; display: flex; align-items: center; gap: 22px; padding: 14px 24px; flex-wrap: wrap; }
.vti-brand { display: flex; align-items: center; gap: 10px; margin-right: auto; color: var(--vti-text) !important; text-decoration: none; font-size: 18px; font-weight: 500; }
.vti-mark { width: 28px; height: 28px; border-radius: var(--vti-r); border: 1px solid var(--vti-accent); display: grid; place-items: center; color: var(--vti-accent); font-size: 17px; }
.vti-links { display: flex; gap: 18px; }
.vti-links a { color: var(--vti-text); text-decoration: none; font-size: 14px; }
.vti-links a:hover, .vti-links a[aria-current] { color: var(--vti-accent); }
.vti-actions { display: flex; align-items: center; gap: 8px; }
.vti-user { display: flex; align-items: center; gap: 8px; font-size: 13px; }
.vti-avatar { width: 28px; height: 28px; border-radius: 50%; background: var(--vti-accent-800); color: var(--vti-accent-100); display: grid; place-items: center; font-size: 12px; }

/* Trang danh sách */
.vti-main { max-width: 1240px; margin: 0 auto; padding: 24px 24px 96px; display: flex; flex-direction: column; gap: 36px; }
.vti-hero { display: flex; flex-direction: column; gap: 8px; max-width: 660px; padding-top: 16px; }
.vti-hero p { margin: 0; font-size: 16px; }
.vti-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 14px; }
.vti-card { display: flex; flex-direction: column; gap: 8px; padding: 16px; border-radius: var(--vti-r); background: var(--vti-surface); box-shadow: var(--vti-shadow-sm); text-decoration: none !important; color: var(--vti-text) !important; transition: box-shadow .15s; }
.vti-card:hover { box-shadow: var(--vti-shadow-md); }
.vti-card-title { font-size: 17px; font-weight: 500; line-height: 1.2; }
.vti-card-body { font-size: 13px; opacity: .8; flex: 1; }
.vti-card-meta { display: flex; flex-wrap: wrap; gap: 12px; font-size: 11px; color: var(--vti-n500); }
.vti-card-meta span { display: inline-flex; align-items: center; gap: 4px; }

/* Trang khoá học */
.vti-course { display: grid; grid-template-columns: minmax(170px, 230px) minmax(0, 1fr); gap: 40px; }
.vti-side { display: flex; flex-direction: column; gap: 2px; padding-top: 22px; }
.vti-side a { padding: 8px 10px; border-radius: var(--vti-r); font-size: 14px; color: var(--vti-text); text-decoration: none; }
.vti-side a:hover { background: color-mix(in srgb, var(--vti-text) 6%, transparent); }
.vti-side a[aria-current] { color: var(--vti-accent); background: color-mix(in srgb, var(--vti-accent) 10%, transparent); }
.vti-content { display: flex; flex-direction: column; gap: 28px; min-width: 0; }
.vti-section { display: flex; flex-direction: column; gap: 2px; }
.vti-row { display: grid; grid-template-columns: 26px minmax(0, 1fr) auto auto; align-items: center; gap: 14px; padding: 10px; border-radius: var(--vti-r); color: var(--vti-text) !important; text-decoration: none !important; }
.vti-row:hover { background: color-mix(in srgb, var(--vti-text) 5%, transparent); }
.vti-row > .ph:first-child { font-size: 18px; color: var(--vti-accent); }
.vti-row.is-locked > .ph:first-child { color: var(--vti-n600); }
.vti-row-main { display: flex; flex-direction: column; min-width: 0; }
.vti-row-title { font-size: 14px; }
.vti-row-sub { font-size: 12px; color: var(--vti-n500); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
@media (max-width: 760px) { .vti-course { grid-template-columns: 1fr; } .vti-side { flex-direction: row; flex-wrap: wrap; padding-top: 0; } .vti-row .vti-tag { display: none; } .vti h1 { font-size: 34px; } }

/* Trang bài giảng toàn màn hình */
body.vti-lesson { height: 100vh; overflow: hidden; display: flex; flex-direction: column; background: #161826 !important; }
.vti-bar { height: 48px; flex: none; display: flex; align-items: center; gap: 8px; padding: 0 10px; box-shadow: 0 1px 0 var(--vti-n800); }
.vti-crumb { display: flex; align-items: center; gap: 8px; min-width: 0; margin-right: auto; font-size: 13px; }
.vti-crumb strong { font-weight: 500; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.vti-crumb .vti-muted { white-space: nowrap; }
.vti-pos { font-size: 12px; white-space: nowrap; }
.vti-bar [data-vti-done] .ph { color: var(--vti-accent); }
.vti-stage { flex: 1; min-height: 0; position: relative; }
.vti-stage iframe { display: block; width: 100%; height: 100%; border: 0; background: #fbfbfd; }
.vti-lock { height: 100%; display: flex; align-items: center; padding: 0 8vw; overflow: auto; }
.vti-lock > div { display: flex; flex-direction: column; align-items: flex-start; gap: 12px; max-width: 520px; padding: 32px 0; }
.vti-lock p { margin: 0; }
.vti-lock-icon { width: 44px; height: 44px; border-radius: var(--vti-r); border: 1px solid var(--vti-accent); display: grid; place-items: center; color: var(--vti-accent); font-size: 22px; }
.vti-row-actions { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 4px; }
.vti-code-form { display: flex; gap: 8px; width: 100%; max-width: 360px; }
.vti-input { flex: 1; min-height: 36px; padding: 6px 10px; font: 14px "Inter", system-ui, sans-serif; color: var(--vti-text); caret-color: var(--vti-accent); background: var(--vti-surface); border: 1px solid var(--vti-divider); border-radius: var(--vti-r); text-transform: uppercase; }
.vti-input:hover { border-color: color-mix(in srgb, var(--vti-text) 45%, transparent); }
.vti-input:focus-visible { border-color: var(--vti-accent); outline-offset: 0; }
.vti-error { color: var(--vti-accent-300); font-size: 13px; }
.vti-google:empty { display: none; }
@media (max-width: 760px) { .vti-crumb .vti-muted, .vti-crumb .ph, .vti-crumb .vti-tag, .vti-pos, .vti-bar .vti-btn span { display: none; } .vti-bar .vti-btn:not(.vti-icon) { width: 34px; height: 34px; padding: 0; } }

.vti-toast { position: fixed; left: 50%; bottom: 20px; transform: translateX(-50%); background: var(--vti-surface); color: var(--vti-text); box-shadow: var(--vti-shadow-lg); padding: 10px 16px; border-radius: var(--vti-r); font: 13px "Inter", system-ui, sans-serif; z-index: 99999; }