A complete header + mega menu built as one wrapper component with nested components, where every layout, design and behaviour option is a prop. Structure: section > "Mega Menu Pro" (wrapper) whose "items" slot holds "Nav Item" components. A Nav Item is a plain link, a classic dropdown or a mega panel; its "panel" slot takes "Column" (title + "links" slot of "Link"), "Feature" cards, "Gallery" ("tiles" slot of "Tile") or, for dropdowns, "Sub Item" entries that nest into flyout submenus through their own "submenu" slot. Wrapper props — brand: showLogo, logo, logoAlt, logoSize, showMark, showBrandName, brandName, homeUrl. Layout: layout (inline|stacked), navAlign (start|center|end), width (content|wide|full), height (compact|regular|tall), style (solid|glass|floating|minimal), theme (light|dark|brand), accent (primary|secondary|accent|neutral), divider. Position and scroll: position (static|sticky|fixed|overlay), onScroll (stay|hide|shrink), transparentTop, scrolledShadow. Desktop menu: trigger (hover|click|both), openDelay, closeDelay, safeZone (intelligent buffer zone so diagonal moves toward a panel never switch menus), dropdownStyle (morph = one surface that glides between panels, adaptive = the header grows to each panel height, cards = a card per panel), animation (slide|fade|scale|rise|none), duration, easing (smooth|spring|snappy|linear), itemHover (pill|underline|roll|text|none), showChevrons, showCaret, dropdownGap, backdrop (none|dim|blur), flyoutSubmenus, closeOnLinkClick, editorOpen (keeps one menu open inside the Etch builder only, for editing). Mobile: breakpoint (px; below it the header switches to mobile mode), mobileStyle (drawer|fullscreen|dropdown), drawerSide (end|start), submenuMode (accordion|drill), multiOpen, backButton (title|back|both), backLabel, swipeToClose, scrollLock, toggleStyle (lines|dots|label), menuLabel, showMobileCta. Actions: showCta, ctaLabel, ctaUrl, ctaStyle (solid|outline|glass|gradient), ctaIcon, showSecondary, secondaryLabel, secondaryUrl, showSearch, searchPlaceholder, searchAction. Accessibility: navLabel. Nav Item props: type (link|dropdown|mega), label, url, target, showIcon + icon, showBadge + badge + badgeTone, highlight (none|accent|pill|gradient|button), panelWidth (auto|s|m|l|xl|container|full), panelAlign (center|start|end), columns (1-5|auto), showIntro + introTitle + introText + introPosition (side|top) + showIntroCta + introCtaLabel + introCtaUrl, showFooter + footerText + footerLinkLabel + footerUrl. Column props: title, showTitle, span (1|2), style (plain|tinted|bordered), linkColumns (1|2). Link props: label, url, target, description + showDescription, icon + showIcon, iconStyle (tile|plain|circle), showBadge + badge + badgeTone, showArrow. Feature props: style (card|cover|minimal), tone (default|accent|dark), span (1|2|row), image + imageAlt + showImage, eyebrow + showEyebrow, title, text + showText, linkLabel, url. Gallery props: title, showTitle, columns (2|3|4|6), ratio (square|landscape|portrait). Tile props: image, imageAlt, label, showLabel, url. Sub Item props: label, url, description + showDescription, icon + showIcon, hasSubmenu. Behaviour (vanilla JS, reads only the data attributes the props write): hover intent with buffer zone, click to pin, ArrowLeft/Right across top items, ArrowDown into a panel and ArrowUp/Down through it, Escape and outside click close and return focus, flyout submenus by hover, focus or their toggle button; mobile drawer/fullscreen/dropdown with accordion or drill-down panels, focus trap, swipe to close and scroll lock; sticky hide-on-scroll and shrink, transparent-at-top, search panel. Unique ids per instance, reduced motion removes movement, AA contrast in every theme, 44px touch targets, forced-colors safe. ?mmp-open=N on the URL opens menu N for screenshots.