[{"data":1,"prerenderedAt":-1},["ShallowReactive",2],{"verticals":3,"playground-overscroll-behavior-scroll-containment":32},[4,20],{"id":5,"slug":6,"name":7,"tagline":8,"description":9,"accentFrom":10,"accentTo":11,"icon":12,"defaultLocale":13,"locales":14,"features":16,"position":19},"019fe637-3d33-714b-b57f-23e163ffca0c","dev","Web Development","Build. Learn. Ship.","Practical courses, engineering-grade articles and open-source tools for people who ship.","violet-500","cyan-400","◇","en",[13,15],"fa",{"courses":17,"paths":17,"articles":17,"exams":18,"flashcards":18,"packages":17,"community":17,"certificates":17,"teams":17,"commerce":17},true,false,0,{"id":21,"slug":22,"name":23,"tagline":24,"description":25,"accentFrom":26,"accentTo":10,"icon":27,"defaultLocale":13,"locales":28,"features":30,"position":31},"019fe637-3dc2-754c-8657-0f175bfee7c6","lang","Languages","Learn a language the way you learn a codebase.","Structured paths, listening drills and spaced repetition that actually sticks.","amber-400","⌘",[13,15,29],"es",{"courses":18,"paths":18,"articles":17,"exams":18,"flashcards":17,"packages":18,"community":17,"certificates":17,"teams":18,"commerce":18},2,{"slug":33,"title":34,"summary":35,"html":36,"css":37,"js":38,"config":39,"doc":41},"overscroll-behavior-scroll-containment","overscroll-behavior — interactive playground",null,"\u003Cdiv class=\"pg\">\n    \u003Ch1 class=\"pg-title\">📜 overscroll-behavior live\u003C\u002Fh1>\n    \u003Cp class=\"pg-sub\">\n      Scroll the \u003Cstrong>inner box\u003C\u002Fstrong> in each panel past its bottom edge and\n      watch what happens to the outer container. On the left, scrolling chains to\n      the parent (default). On the right, \u003Ccode>overscroll-behavior-y: contain\u003C\u002Fcode>\n      stops it.\n    \u003C\u002Fp>\n\n    \u003C!-- Two-up comparison -->\n    \u003Cdiv class=\"two-up\">\n      \u003C!-- LEFT: default \u002F auto -->\n      \u003Cdiv>\n        \u003Cdiv class=\"panel-header\">\n          \u003Cspan class=\"badge badge-bad\">auto (default)\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n        \u003Ccode class=\"css-badge\">overscroll-behavior-y: auto\u003C\u002Fcode>\n        \u003Cdiv class=\"demo-outer\" id=\"outerAuto\">\n          \u003Cdiv class=\"outer-content\">\n            \u003Cspan class=\"top-label\">↑ outer top\u003C\u002Fspan>\n            \u003Cspan style=\"color:var(--muted)\">← outer container scrolls when inner hits its edge\u003C\u002Fspan>\n            \u003Cspan class=\"bottom-label\">↓ outer bottom\u003C\u002Fspan>\n          \u003C\u002Fdiv>\n          \u003Cdiv class=\"demo-inner\" id=\"innerAuto\">\n            \u003Cdiv class=\"inner-content\">\n              \u003Cspan class=\"top-label\">↑ inner top\u003C\u002Fspan>\n              \u003Cspan>scroll me ↕\u003C\u002Fspan>\n              \u003Cspan>scroll further ↕\u003C\u002Fspan>\n              \u003Cspan>scroll further ↕\u003C\u002Fspan>\n              \u003Cspan class=\"bottom-label\">↓ inner bottom — keep scrolling to see chaining\u003C\u002Fspan>\n            \u003C\u002Fdiv>\n          \u003C\u002Fdiv>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"status-row\">\n          \u003Cdiv class=\"status-dot\" id=\"dotAuto\">\u003C\u002Fdiv>\n          \u003Cspan id=\"statusAuto\" style=\"color:var(--muted)\">Scroll the inner box…\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"log-area\" id=\"logAuto\">\n          \u003Cdiv class=\"empty\">Events appear here…\u003C\u002Fdiv>\n        \u003C\u002Fdiv>\n      \u003C\u002Fdiv>\n\n      \u003C!-- RIGHT: contain -->\n      \u003Cdiv>\n        \u003Cdiv class=\"panel-header\">\n          \u003Cspan class=\"badge badge-good\">contain\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n        \u003Ccode class=\"css-badge\">overscroll-behavior-y: contain\u003C\u002Fcode>\n        \u003Cdiv class=\"demo-outer\" id=\"outerContain\">\n          \u003Cdiv class=\"outer-content\">\n            \u003Cspan class=\"top-label\">↑ outer top\u003C\u002Fspan>\n            \u003Cspan style=\"color:var(--muted)\">← outer container stays put when inner hits its edge\u003C\u002Fspan>\n            \u003Cspan class=\"bottom-label\">↓ outer bottom\u003C\u002Fspan>\n          \u003C\u002Fdiv>\n          \u003Cdiv class=\"demo-inner\" id=\"innerContain\" style=\"overscroll-behavior-y: contain;\">\n            \u003Cdiv class=\"inner-content\">\n              \u003Cspan class=\"top-label\">↑ inner top\u003C\u002Fspan>\n              \u003Cspan>scroll me ↕\u003C\u002Fspan>\n              \u003Cspan>scroll further ↕\u003C\u002Fspan>\n              \u003Cspan>scroll further ↕\u003C\u002Fspan>\n              \u003Cspan class=\"bottom-label\">↓ inner bottom — scroll past this edge\u003C\u002Fspan>\n            \u003C\u002Fdiv>\n          \u003C\u002Fdiv>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"status-row\">\n          \u003Cdiv class=\"status-dot\" id=\"dotContain\">\u003C\u002Fdiv>\n          \u003Cspan id=\"statusContain\" style=\"color:var(--muted)\">Scroll the inner box…\u003C\u002Fspan>\n        \u003C\u002Fdiv>\n        \u003Cdiv class=\"log-area\" id=\"logContain\">\n          \u003Cdiv class=\"empty\">Events appear here…\u003C\u002Fdiv>\n        \u003C\u002Fdiv>\n      \u003C\u002Fdiv>\n    \u003C\u002Fdiv>\n\n    \u003C!-- Toggle panel -->\n    \u003Cdiv class=\"panel\" style=\"margin-top:20px\">\n      \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">2\u003C\u002Fspan> Toggle the property live\u003C\u002Fdiv>\n      \u003Cp class=\"label\">Switch \u003Ccode>overscroll-behavior-y\u003C\u002Fcode> on the right inner box to see the difference in real time.\u003C\u002Fp>\n      \u003Cdiv class=\"btn-row\">\n        \u003Cbutton class=\"btn primary sm\" onclick=\"setContain('contain')\">contain\u003C\u002Fbutton>\n        \u003Cbutton class=\"btn sm\" onclick=\"setContain('none')\">none\u003C\u002Fbutton>\n        \u003Cbutton class=\"btn sm\" onclick=\"setContain('auto')\">auto (chain again)\u003C\u002Fbutton>\n      \u003C\u002Fdiv>\n      \u003Cdiv style=\"margin-top:10px;font-family:var(--mono);font-size:0.8rem;color:var(--muted)\">\n        Current value: \u003Cstrong id=\"currentVal\" style=\"color:var(--accent)\">contain\u003C\u002Fstrong>\n      \u003C\u002Fdiv>\n    \u003C\u002Fdiv>\n\n    \u003C!-- The code -->\n    \u003Cdiv class=\"panel\">\n      \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">3\u003C\u002Fspan> The CSS making this work\u003C\u002Fdiv>\n      \u003Cdiv class=\"code\">\u002F* One property stops scroll from escaping the container *\u002F\n.inner-box {\n  overflow-y: auto;\n  overscroll-behavior-y: contain;  \u002F* ← that's it *\u002F\n}\n\n\u002F* Axis-specific variants *\u002F\noverscroll-behavior-x: contain;   \u002F* horizontal *\u002F\noverscroll-behavior:   contain;   \u002F* both axes (shorthand) *\u002F\n\n\u002F* Suppress the overscroll effect entirely *\u002F\noverscroll-behavior-y: none;      \u002F* also kills pull-to-refresh *\u002F\u003C\u002Fdiv>\n    \u003C\u002Fdiv>\n\n    \u003C!-- Comparison table -->\n    \u003Cdiv class=\"panel\">\n      \u003Cdiv class=\"panel-label\">\u003Cspan class=\"n\">4\u003C\u002Fspan> CSS vs JavaScript approach\u003C\u002Fdiv>\n      \u003Ctable class=\"vs-table\">\n        \u003Cthead>\n          \u003Ctr>\n            \u003Cth>Aspect\u003C\u002Fth>\n            \u003Cth class=\"good\">overscroll-behavior: contain\u003C\u002Fth>\n            \u003Cth class=\"bad\">touchmove + preventDefault()\u003C\u002Fth>\n          \u003C\u002Ftr>\n        \u003C\u002Fthead>\n        \u003Ctbody>\n          \u003Ctr>\n            \u003Ctd class=\"row-label\">Code required\u003C\u002Ftd>\n            \u003Ctd class=\"good\">One CSS declaration\u003C\u002Ftd>\n            \u003Ctd class=\"bad\">~15 lines of JS event handling\u003C\u002Ftd>\n          \u003C\u002Ftr>\n          \u003Ctr>\n            \u003Ctd class=\"row-label\">Scroll performance\u003C\u002Ftd>\n            \u003Ctd class=\"good\">Native — no main-thread cost\u003C\u002Ftd>\n            \u003Ctd class=\"bad\">\u003Ccode>passive: false\u003C\u002Fcode> blocks scroll on every touchmove\u003C\u002Ftd>\n          \u003C\u002Ftr>\n          \u003Ctr>\n            \u003Ctd class=\"row-label\">Edge accuracy\u003C\u002Ftd>\n            \u003Ctd class=\"good\">Exact — browser knows its own boundaries\u003C\u002Ftd>\n            \u003Ctd class=\"bad\">Must compare scrollTop, scrollHeight, clientHeight\u003C\u002Ftd>\n          \u003C\u002Ftr>\n          \u003Ctr>\n            \u003Ctd class=\"row-label\">Cleanup\u003C\u002Ftd>\n            \u003Ctd class=\"good\">Nothing — it's a style rule\u003C\u002Ftd>\n            \u003Ctd class=\"bad\">removeEventListener on unmount\u003C\u002Ftd>\n          \u003C\u002Ftr>\n          \u003Ctr>\n            \u003Ctd class=\"row-label\">Pull-to-refresh\u003C\u002Ftd>\n            \u003Ctd class=\"good\">Controllable with \u003Ccode>none\u003C\u002Fcode>\u003C\u002Ftd>\n            \u003Ctd class=\"bad\">Requires separate logic\u003C\u002Ftd>\n          \u003C\u002Ftr>\n        \u003C\u002Ftbody>\n      \u003C\u002Ftable>\n    \u003C\u002Fdiv>\n  \u003C\u002Fdiv>","\u002F*\n * Shared playground design system — daily-post\n * ============================================\n * Link it from any post's playground\u002Findex.html (no per-post boilerplate):\n *\n *   \u003Clink rel=\"stylesheet\" href=\"..\u002F..\u002F..\u002Fplayground\u002Fassets\u002Fbase.css\" \u002F>\n *\n * The relative path resolves the same locally (posts\u002F\u003Cbase>\u002Fplayground\u002F) and on\n * the deployed host (public\u002Fposts\u002F\u003Cbase>\u002Fplayground\u002F), because build-site.js\n * mirrors this file to public\u002Fplayground\u002Fassets\u002Fbase.css. For a CodeSandbox\n * --embed, playground.js inlines this file so the single-file sandbox still styles.\n *\n * Then write ONLY the demo-specific CSS in your inline \u003Cstyle>. Everything below\n * — tokens, layout, panels, buttons, toggles, sliders, code blocks, status\u002Flog,\n * banners, presets — comes for free and looks consistent across every post.\n *\n * Theme-aware: dark by default, light via prefers-color-scheme AND a\n * [data-theme] override on \u003Chtml> (so a toggle can force either). Accessible:\n * real focus rings, adequate contrast, reduced-motion honored.\n *\u002F\n\n\u002F* ---------- design tokens ---------- *\u002F\n:root {\n  --bg: #0d1117;\n  --bg-grid: #ffffff0a;\n  --panel: #161b22;\n  --panel-2: #0b0e14;\n  --card: #0b0e14;\n  --ink: #e8ebf2;\n  --muted: #9aa4b2;\n  --faint: #6b7688;\n  --line: #232a35;\n  --line-soft: #ffffff12;\n  --accent: #7c9cff;\n  --accent-ink: #0b0e14;\n  --good: #3fb950;\n  --warn: #f0883e;\n  --bad: #f85149;\n  --info: #58a6ff;\n  --radius: 14px;\n  --radius-sm: 9px;\n  --shadow: 0 8px 30px #0006;\n  --shadow-sm: 0 4px 14px #0005;\n  --mono: ui-monospace, SFMono-Regular, \"SF Mono\", Menlo, Consolas, \"Liberation Mono\", monospace;\n  --sans: ui-sans-serif, system-ui, -apple-system, \"Segoe UI\", Roboto, \"Helvetica Neue\", sans-serif;\n  color-scheme: dark;\n}\n\n\u002F* Light theme — system preference, overridable by [data-theme] on \u003Chtml>. *\u002F\n@media (prefers-color-scheme: light) {\n  :root:not([data-theme=\"dark\"]) {\n    --bg: #f4f6fb;\n    --bg-grid: #00000008;\n    --panel: #ffffff;\n    --panel-2: #f0f3f9;\n    --card: #f7f9fc;\n    --ink: #131722;\n    --muted: #5b6472;\n    --faint: #8a93a3;\n    --line: #e2e7f0;\n    --line-soft: #00000010;\n    --accent: #2f6df0;\n    --accent-ink: #ffffff;\n    --good: #1a7f37;\n    --warn: #bc4c00;\n    --bad: #cf222e;\n    --info: #0969da;\n    --shadow: 0 8px 30px #0000001f;\n    --shadow-sm: 0 4px 14px #00000014;\n    color-scheme: light;\n  }\n}\n:root[data-theme=\"light\"] {\n  --bg: #f4f6fb;\n  --bg-grid: #00000008;\n  --panel: #ffffff;\n  --panel-2: #f0f3f9;\n  --card: #f7f9fc;\n  --ink: #131722;\n  --muted: #5b6472;\n  --faint: #8a93a3;\n  --line: #e2e7f0;\n  --line-soft: #00000010;\n  --accent: #2f6df0;\n  --accent-ink: #ffffff;\n  --good: #1a7f37;\n  --warn: #bc4c00;\n  --bad: #cf222e;\n  --info: #0969da;\n  --shadow: 0 8px 30px #0000001f;\n  --shadow-sm: 0 4px 14px #00000014;\n  color-scheme: light;\n}\n\n\u002F* ---------- reset & base ---------- *\u002F\n*, *::before, *::after { box-sizing: border-box; }\n\nbody {\n  margin: 0;\n  min-height: 100vh;\n  font-family: var(--sans);\n  color: var(--ink);\n  background:\n    radial-gradient(circle at 1px 1px, var(--bg-grid) 1px, transparent 0) 0 0 \u002F 24px 24px,\n    var(--bg);\n  display: flex;\n  justify-content: center;\n  align-items: flex-start;\n  padding: clamp(14px, 3vw, 26px);\n  line-height: 1.55;\n  -webkit-font-smoothing: antialiased;\n  text-rendering: optimizeLegibility;\n}\n\n\u002F* The single content column. *\u002F\n.pg {\n  width: 100%;\n  max-width: 860px;\n}\n\n\u002F* ---------- header ---------- *\u002F\n.pg-title {\n  font-size: clamp(1.15rem, 1rem + 1vw, 1.4rem);\n  font-weight: 800;\n  letter-spacing: -0.02em;\n  margin: 0 0 4px;\n  display: flex;\n  align-items: center;\n  gap: 9px;\n}\n.pg-sub {\n  color: var(--muted);\n  font-size: 0.92rem;\n  line-height: 1.5;\n  margin: 0 0 16px;\n  max-width: 66ch;\n}\n.pg-sub strong, .pg-sub b { color: var(--ink); font-weight: 700; }\n.pg-sub code { font-family: var(--mono); background: var(--line-soft); color: var(--accent);\n  padding: 1px 6px; border-radius: 6px; font-size: 0.85em; }\n\n\u002F* ---------- panels ---------- *\u002F\n.panel {\n  background: var(--panel);\n  border: 1px solid var(--line);\n  border-radius: var(--radius);\n  padding: 16px 18px;\n  margin-bottom: 14px;\n  box-shadow: var(--shadow-sm);\n}\n.panel-label {\n  font-size: 0.7rem;\n  text-transform: uppercase;\n  letter-spacing: 0.08em;\n  color: var(--muted);\n  font-weight: 800;\n  margin: 0 0 13px;\n  display: flex;\n  align-items: center;\n  gap: 8px;\n}\n.panel-label .n {\n  display: inline-grid; place-items: center;\n  width: 18px; height: 18px; border-radius: 50%;\n  background: var(--accent); color: var(--accent-ink);\n  font-size: 0.66rem; font-weight: 800;\n}\n\n\u002F* ---------- layout helpers ---------- *\u002F\n.row { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; }\n.row.between { justify-content: space-between; }\n.col { display: flex; flex-direction: column; gap: 10px; }\n.grow { flex: 1 1 0; min-width: 0; }\n.wrap-controls { display: flex; flex-wrap: wrap; gap: 16px 24px; align-items: flex-end; }\n.field { display: flex; flex-direction: column; gap: 7px; min-width: 0; }\n.field > .label, .ctl-label {\n  font-size: 0.7rem; text-transform: uppercase; letter-spacing: 0.04em;\n  color: var(--muted); font-weight: 800;\n}\n\n\u002F* ---------- buttons ---------- *\u002F\n.btn {\n  font: inherit; font-weight: 650; font-size: 0.88rem;\n  cursor: pointer; user-select: none;\n  border: 1px solid var(--line);\n  background: var(--card); color: var(--ink);\n  padding: 9px 15px; border-radius: var(--radius-sm);\n  display: inline-flex; align-items: center; gap: 8px;\n  transition: background .15s ease, border-color .15s ease, transform .05s ease, color .15s ease;\n}\n.btn:hover { background: var(--line-soft); border-color: var(--muted); }\n.btn:active { transform: translateY(1px); }\n.btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }\n.btn[disabled] { opacity: 0.45; cursor: not-allowed; }\n.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }\n.btn.primary:hover { filter: brightness(1.08); background: var(--accent); }\n.btn.good { background: var(--good); border-color: var(--good); color: #04140a; }\n.btn.bad  { background: var(--bad);  border-color: var(--bad);  color: #fff; }\n.btn.ghost { background: transparent; }\n.btn.sm { padding: 6px 11px; font-size: 0.82rem; }\n\n.btn-row { display: flex; flex-wrap: wrap; gap: 9px; }\n\n\u002F* Segmented control — a row of buttons where one is active (aria-pressed). *\u002F\n.seg { display: inline-flex; background: var(--card); border: 1px solid var(--line);\n  border-radius: var(--radius-sm); padding: 3px; gap: 3px; }\n.seg button {\n  font: inherit; font-weight: 650; font-size: 0.84rem; cursor: pointer;\n  border: none; background: transparent; color: var(--muted);\n  padding: 7px 13px; border-radius: 7px;\n  transition: background .15s ease, color .15s ease;\n}\n.seg button:hover { color: var(--ink); }\n.seg button[aria-pressed=\"true\"] { background: var(--accent); color: var(--accent-ink); }\n.seg button:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }\n\n\u002F* Preset chips — worked-example shortcuts. *\u002F\n.presets { display: flex; flex-wrap: wrap; gap: 8px; }\n.presets .btn { background: var(--panel-2); }\n\n\u002F* ---------- toggle switch ---------- *\u002F\n.toggle { display: inline-flex; align-items: center; gap: 10px; cursor: pointer;\n  font-size: 0.88rem; font-weight: 600; user-select: none; }\n.toggle input { position: absolute; opacity: 0; width: 0; height: 0; }\n.switch { position: relative; width: 44px; height: 25px; border-radius: 999px; flex: none;\n  background: var(--line); border: 1px solid var(--line); transition: background .18s ease; }\n.switch::after { content: \"\"; position: absolute; top: 2px; left: 2px; width: 19px; height: 19px;\n  border-radius: 50%; background: #cfd6e4; transition: transform .18s ease; box-shadow: 0 1px 3px #0006; }\n.toggle input:checked + .switch { background: var(--good); border-color: var(--good); }\n.toggle input:checked + .switch::after { transform: translateX(19px); background: #fff; }\n.toggle input:focus-visible + .switch { outline: 2px solid var(--accent); outline-offset: 2px; }\n\n\u002F* ---------- range slider ---------- *\u002F\ninput[type=\"range\"] {\n  -webkit-appearance: none; appearance: none; width: 100%; height: 6px;\n  background: var(--line); border-radius: 999px; outline: none; cursor: pointer; margin: 8px 0;\n}\ninput[type=\"range\"]::-webkit-slider-thumb {\n  -webkit-appearance: none; appearance: none; width: 19px; height: 19px; border-radius: 50%;\n  background: var(--accent); border: 2px solid var(--panel); box-shadow: var(--shadow-sm); cursor: pointer;\n}\ninput[type=\"range\"]::-moz-range-thumb {\n  width: 19px; height: 19px; border-radius: 50%; background: var(--accent);\n  border: 2px solid var(--panel); box-shadow: var(--shadow-sm); cursor: pointer;\n}\ninput[type=\"range\"]:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; }\n\n\u002F* ---------- text inputs \u002F selects ---------- *\u002F\ninput[type=\"text\"], input[type=\"number\"], input[type=\"search\"], select, textarea {\n  font: inherit; color: var(--ink); background: var(--card);\n  border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 8px 11px; width: 100%;\n}\ntextarea { font-family: var(--mono); font-size: 0.85rem; line-height: 1.6; resize: vertical; }\ninput:focus-visible, select:focus-visible, textarea:focus-visible {\n  outline: 2px solid var(--accent); outline-offset: 1px; border-color: var(--accent);\n}\n\n\u002F* ---------- status \u002F output \u002F log ---------- *\u002F\n.status {\n  display: flex; align-items: center; gap: 9px; flex-wrap: wrap;\n  font-size: 0.9rem; font-weight: 600;\n  padding: 11px 14px; border-radius: var(--radius-sm);\n  background: var(--panel-2); border: 1px solid var(--line); color: var(--ink);\n}\n.status.good { border-color: color-mix(in srgb, var(--good) 55%, var(--line)); }\n.status.warn { border-color: color-mix(in srgb, var(--warn) 55%, var(--line)); }\n.status.bad  { border-color: color-mix(in srgb, var(--bad) 55%, var(--line)); }\n.dot { width: 9px; height: 9px; border-radius: 50%; background: var(--muted); flex: none; }\n.dot.good { background: var(--good); } .dot.warn { background: var(--warn); }\n.dot.bad { background: var(--bad); } .dot.info { background: var(--info); }\n\n.output { background: var(--panel-2); border: 1px solid var(--line); border-radius: var(--radius-sm);\n  padding: 13px 15px; }\n.log { font-family: var(--mono); font-size: 0.8rem; line-height: 1.7; background: var(--card);\n  border: 1px solid var(--line); border-radius: var(--radius-sm); padding: 11px 14px;\n  max-height: 220px; overflow-y: auto; white-space: pre-wrap; }\n\n\u002F* ---------- code block + syntax tokens ---------- *\u002F\n.code {\n  font-family: var(--mono); font-size: 0.82rem; line-height: 1.7;\n  background: var(--panel-2); border: 1px solid var(--line); border-radius: var(--radius-sm);\n  padding: 13px 15px; overflow-x: auto; white-space: pre; tab-size: 2;\n}\n.code .tok-sel  { color: var(--accent); }\n.code .tok-prop { color: #86e29b; }\n.code .tok-kw   { color: #ff9bcb; }\n.code .tok-str  { color: #f0c674; }\n.code .tok-num  { color: #f0883e; }\n.code .tok-cmt  { color: var(--faint); font-style: italic; }\n.code .hl { background: color-mix(in srgb, var(--good) 22%, transparent); border-radius: 4px; padding: 0 3px; }\n\n\u002F* ---------- hint \u002F caption ---------- *\u002F\n.hint { font-size: 0.83rem; color: var(--muted); line-height: 1.55; margin: 10px 0 0; }\n.hint code { font-family: var(--mono); color: var(--ink); background: var(--line-soft);\n  padding: 1px 5px; border-radius: 5px; font-size: 0.86em; }\n.hint strong { color: var(--ink); }\n\n\u002F* ---------- banner (feature-support \u002F notices) ---------- *\u002F\n.banner {\n  display: none; margin-bottom: 14px; padding: 11px 14px; border-radius: 11px;\n  font-size: 0.85rem; line-height: 1.5;\n  color: var(--ink); background: color-mix(in srgb, var(--warn) 12%, var(--panel));\n  border: 1px solid color-mix(in srgb, var(--warn) 45%, var(--line));\n}\n.banner.show { display: block; }\n.banner.info { background: color-mix(in srgb, var(--info) 12%, var(--panel));\n  border-color: color-mix(in srgb, var(--info) 45%, var(--line)); }\n.banner code { font-family: var(--mono); background: var(--line-soft); padding: 1px 5px; border-radius: 5px; }\n\n\u002F* ---------- misc atoms ---------- *\u002F\n.pill { display: inline-flex; align-items: center; gap: 6px; font-size: 0.75rem; font-weight: 700;\n  padding: 3px 9px; border-radius: 999px; background: var(--line-soft); color: var(--muted); }\n.pill.good { color: var(--good); background: color-mix(in srgb, var(--good) 16%, transparent); }\n.pill.bad  { color: var(--bad);  background: color-mix(in srgb, var(--bad) 16%, transparent); }\n.mono { font-family: var(--mono); }\n.muted { color: var(--muted); }\n.big-num { font-family: var(--mono); font-size: 1.6rem; font-weight: 800; letter-spacing: -0.02em; }\n\n\u002F* Optional theme toggle button (top-right). Wire it in JS if you want it. *\u002F\n.theme-btn { position: fixed; top: 12px; right: 12px; z-index: 20; }\n\n\u002F* ---------- responsive ---------- *\u002F\n@media (max-width: 560px) {\n  .panel { padding: 14px; }\n  .wrap-controls { gap: 14px; }\n  .btn { padding: 9px 13px; }\n}\n\n\u002F* ---------- reduced motion ---------- *\u002F\n@media (prefers-reduced-motion: reduce) {\n  *, *::before, *::after { transition-duration: 0.01ms !important; animation-duration: 0.01ms !important; }\n}\n\n\n.demo-outer {\n    background: var(--panel-2);\n    border: 2px solid var(--line);\n    border-radius: var(--radius-sm);\n    height: 200px;\n    overflow-y: scroll;\n    position: relative;\n    transition: background 0.2s;\n  }\n  .demo-outer.chained {\n    background: color-mix(in srgb, var(--bad) 12%, var(--panel-2));\n  }\n  .demo-outer.contained {\n    background: color-mix(in srgb, var(--good) 12%, var(--panel-2));\n  }\n\n  .demo-inner {\n    background: color-mix(in srgb, var(--accent) 10%, var(--bg));\n    border: 2px dashed var(--accent);\n    border-radius: 6px;\n    height: 120px;\n    overflow-y: scroll;\n    padding: 10px 12px;\n    margin: 12px;\n    position: relative;\n  }\n  .demo-inner .inner-content {\n    height: 280px;\n    display: flex;\n    flex-direction: column;\n    justify-content: space-between;\n    font-family: var(--mono);\n    font-size: 0.78rem;\n    color: var(--muted);\n  }\n  .demo-inner .inner-content .top-label {\n    color: var(--good);\n    font-weight: 600;\n  }\n  .demo-inner .inner-content .bottom-label {\n    color: var(--bad);\n    font-weight: 600;\n  }\n\n  .outer-content {\n    height: 500px;\n    padding: 12px;\n    font-family: var(--mono);\n    font-size: 0.78rem;\n    color: var(--muted);\n    display: flex;\n    flex-direction: column;\n    justify-content: space-between;\n  }\n  .outer-content .top-label { color: var(--good); font-weight: 600; }\n  .outer-content .bottom-label { color: var(--bad); font-weight: 600; }\n\n  .two-up {\n    display: grid;\n    grid-template-columns: 1fr 1fr;\n    gap: 16px;\n    margin-top: 8px;\n  }\n\n  .panel-header {\n    display: flex;\n    align-items: center;\n    gap: 8px;\n    margin-bottom: 8px;\n    font-size: 0.82rem;\n    font-weight: 700;\n  }\n  .panel-header .badge {\n    font-size: 0.68rem;\n    padding: 2px 8px;\n    border-radius: 20px;\n    font-weight: 800;\n    letter-spacing: 0.04em;\n  }\n  .badge-bad  { background: color-mix(in srgb, var(--bad)  18%, transparent); color: var(--bad); }\n  .badge-good { background: color-mix(in srgb, var(--good) 18%, transparent); color: var(--good); }\n\n  .status-row {\n    display: flex;\n    align-items: center;\n    gap: 8px;\n    margin-top: 8px;\n    font-size: 0.78rem;\n    min-height: 24px;\n  }\n  .status-dot {\n    width: 10px; height: 10px;\n    border-radius: 50%;\n    background: var(--line);\n    flex-shrink: 0;\n    transition: background 0.3s;\n  }\n  .status-dot.chained  { background: var(--bad); }\n  .status-dot.ok       { background: var(--good); }\n\n  .css-badge {\n    font-family: var(--mono);\n    font-size: 0.75rem;\n    background: var(--panel-2);\n    border: 1px solid var(--line);\n    border-radius: 4px;\n    padding: 2px 8px;\n    color: var(--accent);\n    white-space: nowrap;\n  }\n\n  .log-area {\n    margin-top: 8px;\n    background: var(--bg);\n    border: 1px solid var(--line);\n    border-radius: var(--radius-sm);\n    padding: 6px 10px;\n    font-family: var(--mono);\n    font-size: 0.75rem;\n    min-height: 44px;\n    max-height: 100px;\n    overflow-y: auto;\n  }\n  .log-area .log-entry {\n    padding: 2px 0;\n    border-bottom: 1px solid var(--line-soft);\n    animation: fadein 0.2s ease;\n  }\n  .log-area .log-entry:last-child { border-bottom: none; }\n  @keyframes fadein { from { opacity: 0; } to { opacity: 1; } }\n  .log-area .empty { color: var(--faint); font-style: italic; }\n  .chain-event { color: var(--bad); }\n  .ok-event    { color: var(--good); }\n\n.vs-table { width: 100%; border-collapse: collapse; font-size: 0.78rem; }\n  .vs-table th {\n    font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.06em;\n    font-weight: 800; color: var(--muted); padding: 6px 10px;\n    text-align: left; border-bottom: 1px solid var(--line);\n  }\n  .vs-table td {\n    padding: 7px 10px; border-bottom: 1px solid var(--line-soft);\n    vertical-align: top; line-height: 1.5; color: var(--ink);\n  }\n  .vs-table tr:last-child td { border-bottom: none; }\n  .vs-table .row-label { color: var(--muted); font-weight: 600; min-width: 8ch; }\n  .vs-table .good { color: var(--good); }\n  .vs-table .bad  { color: var(--bad); }\n  .vs-table code { font-family: var(--mono); font-size: 0.78em; background: var(--panel-2); padding: 1px 4px; border-radius: 3px; }","const outerAuto    = document.getElementById('outerAuto');\n  const outerContain = document.getElementById('outerContain');\n  const innerAuto    = document.getElementById('innerAuto');\n  const innerContain = document.getElementById('innerContain');\n\n  let autoCount    = 0;\n  let containCount = 0;\n\n  function log(logId, text, cls) {\n    const area = document.getElementById(logId);\n    const empty = area.querySelector('.empty');\n    if (empty) empty.remove();\n    const entry = document.createElement('div');\n    entry.className = `log-entry ${cls}`;\n    entry.textContent = text;\n    area.insertBefore(entry, area.firstChild);\n  }\n\n  function atBottom(el) {\n    return el.scrollTop >= el.scrollHeight - el.clientHeight - 2;\n  }\n\n  function atTop(el) {\n    return el.scrollTop \u003C= 2;\n  }\n\n  \u002F\u002F Track outer scroll — if it moves while inner is at its edge, that's chaining\n  let lastOuterAutoScroll = 0;\n  outerAuto.addEventListener('scroll', () => {\n    if (outerAuto.scrollTop !== lastOuterAutoScroll) {\n      const dot = document.getElementById('dotAuto');\n      const status = document.getElementById('statusAuto');\n      dot.className = 'status-dot chained';\n      status.textContent = 'Scroll chained to outer container!';\n      status.style.color = 'var(--bad)';\n      outerAuto.classList.add('chained');\n      setTimeout(() => {\n        outerAuto.classList.remove('chained');\n        status.textContent = 'Scroll the inner box again…';\n        status.style.color = 'var(--muted)';\n        dot.className = 'status-dot';\n      }, 1500);\n      autoCount++;\n      log('logAuto', `Chain #${autoCount}: outer scrollTop = ${Math.round(outerAuto.scrollTop)}px`, 'chain-event');\n      lastOuterAutoScroll = outerAuto.scrollTop;\n    }\n  });\n\n  let lastOuterContainScroll = 0;\n  outerContain.addEventListener('scroll', () => {\n    if (outerContain.scrollTop !== lastOuterContainScroll) {\n      containCount++;\n      log('logContain', `Outer scrolled anyway: scrollTop = ${Math.round(outerContain.scrollTop)}px (check overscroll-behavior value)`, 'chain-event');\n      lastOuterContainScroll = outerContain.scrollTop;\n    }\n  });\n\n  innerContain.addEventListener('scroll', () => {\n    const dot = document.getElementById('dotContain');\n    const status = document.getElementById('statusContain');\n    if (atBottom(innerContain)) {\n      dot.className = 'status-dot ok';\n      status.textContent = 'At bottom — outer stays put!';\n      status.style.color = 'var(--good)';\n    } else if (atTop(innerContain)) {\n      dot.className = 'status-dot ok';\n      status.textContent = 'At top — outer stays put!';\n      status.style.color = 'var(--good)';\n    } else {\n      dot.className = 'status-dot';\n      status.textContent = 'Scrolling inner…';\n      status.style.color = 'var(--muted)';\n    }\n    if (atBottom(innerContain) || atTop(innerContain)) {\n      log('logContain', `Inner hit edge — outer did NOT scroll (contained!)`, 'ok-event');\n    }\n  });\n\n  function setContain(val) {\n    innerContain.style.overscrollBehaviorY = val;\n    document.getElementById('currentVal').textContent = val;\n    log('logContain', `overscroll-behavior-y changed to \"${val}\"`, 'ok-event');\n  }",{"height":40,"autorun":17},520,{"slug":33,"title":42,"excerpt":43,"coverUrl":44},"You're blocking touchmove events to contain scroll. `overscroll-behavior` does it natively.","When a scrollable container hits its edge, the page behind it starts scrolling too. Developers block this with JavaScript event handlers or body overflow tricks. overscroll-behavior is the CSS property that turns off scroll chaining in one line.","\u002Fmedia\u002Fcovers\u002Foverscroll-behavior-scroll-containment.png"]