diff --git a/components/download/DownloadExperience.tsx b/components/download/DownloadExperience.tsx
index 7fc9b25..c0a52aa 100644
--- a/components/download/DownloadExperience.tsx
+++ b/components/download/DownloadExperience.tsx
@@ -45,7 +45,7 @@ function OsTabs({
                         aria-selected={active}
                         onClick={() => onSelect(os)}
                         className={classNames(
-                            "flex flex-1 items-center justify-center gap-2 px-4 py-3 font-display text-sm font-semibold uppercase tracking-label transition-colors",
+                            "flex flex-1 items-center justify-center gap-1.5 px-2 py-3 font-display text-xs font-semibold uppercase tracking-label transition-colors sm:gap-2 sm:px-4 sm:text-sm",
                             "focus:outline-none focus-visible:ring-2 focus-visible:ring-accent focus-visible:ring-inset",
                             active
                                 ? "border-b-2 border-accent bg-primary/15 text-accent"
@@ -54,7 +54,11 @@ function OsTabs({
                     >
                         <Icon className="h-4 w-4" aria-hidden />
                         <span>{label}</span>
-                        {os === detected && <Badge tone="info">Detected</Badge>}
+                        {os === detected && (
+                            <Badge tone="info" className="hidden sm:inline-flex">
+                                Detected
+                            </Badge>
+                        )}
                     </button>
                 );
             })}
diff --git a/components/home/Hero.tsx b/components/home/Hero.tsx
index 79fe451..e368278 100644
--- a/components/home/Hero.tsx
+++ b/components/home/Hero.tsx
@@ -7,7 +7,7 @@ import ScreenshotFeed from "./ScreenshotFeed";
 export default function Hero() {
     return (
         <section className="mx-auto flex min-h-[calc(100svh-3.5rem)] w-full max-w-[88rem] flex-col justify-center px-4 pb-14 pt-20 sm:px-6 lg:py-16">
-            <div className="grid items-center gap-12 lg:grid-cols-2 lg:gap-10 xl:grid-cols-[minmax(0,10fr)_minmax(0,11fr)] xl:gap-14">
+            <div className="grid grid-cols-1 items-center gap-12 lg:grid-cols-2 lg:gap-10 xl:grid-cols-[minmax(0,10fr)_minmax(0,11fr)] xl:gap-14">
                 {/* Title column */}
                 <div className="flex flex-col items-center text-center lg:items-start lg:text-left">
                     <div className="relative animate-fade-up">
@@ -40,8 +40,7 @@ export default function Hero() {
                     </div>
                 </div>
 
-                {/* screenshot feed */}
-                <div className="relative w-full animate-fade-up [animation-delay:360ms] lg:-mr-6 lg:w-auto">
+                <div className="relative w-full animate-fade-up [animation-delay:360ms] lg:w-auto">
                     <ScreenshotFeed />
                 </div>
             </div>
diff --git a/components/home/RotatingTagline.tsx b/components/home/RotatingTagline.tsx
index 429bab2..985f45c 100644
--- a/components/home/RotatingTagline.tsx
+++ b/components/home/RotatingTagline.tsx
@@ -32,7 +32,7 @@ export default function RotatingTagline() {
     }, []);
 
     return (
-        <p className="splash-text pointer-events-none absolute -top-9 left-0 z-10 max-w-64 text-center font-display text-sm font-semibold leading-tight text-warning [text-shadow:2px_2px_0_rgb(var(--c-void)/0.95)] sm:-left-4 sm:-top-8">
+        <p className="splash-text pointer-events-none absolute -top-9 left-0 z-10 max-w-64 text-center font-display text-sm font-semibold leading-tight text-warning [text-shadow:2px_2px_0_rgb(var(--c-void)/0.95)] sm:-left-4 sm:-top-8 lg:left-0">
             {tagline}
         </p>
     );
diff --git a/components/ui/ButtonGroup.tsx b/components/ui/ButtonGroup.tsx
index 83e0642..60caac6 100644
--- a/components/ui/ButtonGroup.tsx
+++ b/components/ui/ButtonGroup.tsx
@@ -15,7 +15,8 @@ export default function ButtonGroup({ className, children, ...rest }: Props) {
         <div
             role="group"
             className={classNames(
-                "flex divide-x divide-seam overflow-hidden rounded-md",
+                "flex flex-col divide-y divide-seam overflow-hidden rounded-md",
+                "min-[480px]:flex-row min-[480px]:divide-x min-[480px]:divide-y-0",
                 "border border-seam bg-steel shadow-bevel",
                 "[&>*]:flex-1 [&>*]:rounded-none",
                 // keep focus rings visible inside the clipped container
diff --git a/cypress/e2e/responsive.cy.ts b/cypress/e2e/responsive.cy.ts
new file mode 100644
index 0000000..9e8e793
--- /dev/null
+++ b/cypress/e2e/responsive.cy.ts
@@ -0,0 +1,124 @@
+/*
+ * Test if any route has unintended horizontal overflow at most common screens
+ */
+const WIDTHS = [320, 393, 640, 768, 1024];
+
+type Offender = { tag: string; cls: string; left: number; right: number };
+
+/** Elements sticking out horizontally at the current viewport width. */
+function findOverflowingElements(win: Window): Offender[] {
+    const doc = win.document;
+    const vw = doc.documentElement.clientWidth;
+    const offenders: Offender[] = [];
+
+    for (const el of Array.from(doc.querySelectorAll<HTMLElement>("body *"))) {
+        const rect = el.getBoundingClientRect();
+        if (rect.width === 0 && rect.height === 0) continue;
+        if (rect.right <= vw + 1 && rect.left >= -1) continue;
+
+        // Fixed overlays (parallax space, the clown's cage) clip themselves.
+        if (win.getComputedStyle(el).position === "fixed") continue;
+
+        // Skip elements an ancestor already clips or scrolls horizontally
+        let ancestor = el.parentElement;
+        let clipped = false;
+        while (ancestor && ancestor !== doc.body) {
+            if (/(hidden|clip|auto|scroll)/.test(win.getComputedStyle(ancestor).overflowX)) {
+                clipped = true;
+                break;
+            }
+            ancestor = ancestor.parentElement;
+        }
+        if (clipped) continue;
+
+        const cls = typeof el.className === "string" ? el.className : "";
+        offenders.push({
+            tag: el.tagName.toLowerCase(),
+            cls: cls.slice(0, 100),
+            left: Math.round(rect.left),
+            right: Math.round(rect.right),
+        });
+    }
+    return offenders;
+}
+
+function assertNoHorizontalOverflow(route: string) {
+    for (const width of WIDTHS) {
+        cy.viewport(width, 850);
+        // let the resize propagate and media queries re-evaluate
+        cy.wait(100);
+        cy.window().then((win) => {
+            const offenders = findOverflowingElements(win);
+            expect(
+                offenders,
+                `${route} @ ${width}px  elements past the viewport edge:\n` +
+                    JSON.stringify(offenders, null, 2),
+            ).to.have.length(0);
+            expect(
+                win.document.documentElement.scrollWidth,
+                `${route} @ ${width}px  page scroll width`,
+            ).to.be.at.most(width + 1);
+        });
+    }
+}
+
+describe("Responsive layout", () => {
+    it("home has no horizontal overflow at any width", () => {
+        cy.visit("/");
+        cy.contains("h1", "Unitystation!").should("be.visible");
+        assertNoHorizontalOverflow("/");
+    });
+
+    it("download has no horizontal overflow at any width", () => {
+        cy.visit("/download");
+        cy.contains("h1", "Download Pudu Launcher").should("be.visible");
+        assertNoHorizontalOverflow("/download");
+    });
+
+    it("blog has no horizontal overflow at any width", () => {
+        cy.intercept("GET", /changelog\.unitystation\.org\/posts\/\?page=1$/, {
+            fixture: "blogPosts-page1.json",
+        }).as("postsPage1");
+        cy.intercept("GET", /changelog\.unitystation\.org\/posts\/\?page=2$/, {
+            fixture: "blogPosts-page2.json",
+        }).as("postsPage2");
+
+        cy.visit("/blog");
+        cy.wait("@postsPage1");
+        cy.contains("h2", "Station reactor now explodes properly").should("be.visible");
+        // materialise the infinite-scroll page before scanning
+        cy.scrollTo("bottom");
+        cy.wait("@postsPage2");
+        assertNoHorizontalOverflow("/blog");
+    });
+
+    it("changelog has no horizontal overflow at any width", () => {
+        cy.intercept("GET", /changelog\.unitystation\.org\/all-changes/, {
+            fixture: "changelog-page1.json",
+        }).as("changelog");
+
+        cy.visit("/changelog");
+        cy.wait("@changelog");
+        assertNoHorizontalOverflow("/changelog");
+    });
+
+    it("ledger has no horizontal overflow at any width", () => {
+        cy.intercept("GET", /ledger\.unitystation\.org\/movements\/$/, {
+            fixture: "ledger-page1.json",
+        }).as("ledgerPage1");
+
+        cy.visit("/ledger");
+        cy.wait("@ledgerPage1");
+        assertNoHorizontalOverflow("/ledger");
+    });
+
+    for (const route of ["/login", "/register", "/reset-password"]) {
+        it(`${route} has no horizontal overflow at any width`, () => {
+            cy.visit(route);
+            cy.get("h1").should("be.visible");
+            assertNoHorizontalOverflow(route);
+        });
+    }
+});
+
+export {};
diff --git a/next.config.js b/next.config.js
index a365f31..cf9e4b0 100644
--- a/next.config.js
+++ b/next.config.js
@@ -2,6 +2,10 @@
 
 module.exports = {
     reactCompiler: true,
+    // Dev only: lets phones on the home network open the dev server via the
+    // machine's LAN IP. Without this Next blocks its /_next dev resources for
+    // non-localhost origins and pages render but never hydrate (dead buttons).
+    allowedDevOrigins: ["192.168.1.*"],
     images: {
         remotePatterns: [
             {