diff --git a/src/assets/javascripts/component/container/index.ts b/src/assets/javascripts/component/container/index.ts
index c1c667e6c..5c7839c15 100644
--- a/src/assets/javascripts/component/container/index.ts
+++ b/src/assets/javascripts/component/container/index.ts
@@ -20,12 +20,10 @@
  * IN THE SOFTWARE.
  */
 
-import { reduce } from "ramda"
 import { Observable, combineLatest } from "rxjs"
 import { distinctUntilChanged, map, shareReplay } from "rxjs/operators"
 
 import { ViewportOffset, ViewportSize } from "../../ui"
-import { toArray } from "../../utilities"
 
 /* ----------------------------------------------------------------------------
  * Types
@@ -72,41 +70,40 @@ export function fromContainer(
   container: HTMLElement, header: HTMLElement, { size$, offset$ }: Options
 ): Observable<Container> {
 
-  /* Adjust top offset if header is fixed */
+  /* Adjust for header offset if fixed */
   const adjust = getComputedStyle(header)
     .getPropertyValue("position") === "fixed"
       ? header.offsetHeight
       : 0
 
-  /* Compute the container's top offset */
-  const top$ = size$.pipe(
-    map(() => reduce((offset, child) => {
-      return Math.max(offset, child.offsetTop)
-    }, 0, toArray(container.children)) - adjust),
-    distinctUntilChanged(),
-    shareReplay({ bufferSize: 1, refCount: true })
-  )
-
   /* Compute the container's available height */
-  const height$ = combineLatest(offset$, size$, top$).pipe(
-    map(([{ y }, { height }, offset]) => {
-      const bottom = container.offsetTop + container.offsetHeight
-      return height - adjust
-        - Math.max(0, offset - y)
-        - Math.max(0, height + y - bottom)
-    }),
-    distinctUntilChanged()
-  )
+  const height$ = combineLatest(offset$, size$)
+    .pipe(
+      map(([{ y }, { height }]) => {
+        const top    = container.offsetTop
+        const bottom = container.offsetHeight + top
+        return height
+          - Math.max(0, top    - y,  adjust)
+          - Math.max(0, height + y - bottom)
+      }),
+      distinctUntilChanged()
+    )
 
   /* Compute whether the viewport offset is past the container's top */
-  const active$ = combineLatest(offset$, top$).pipe(
-    map(([{ y }, threshold]) => y >= threshold),
-    distinctUntilChanged()
-  )
+  const active$ = offset$
+    .pipe(
+      map(({ y }) => y >= container.offsetTop - adjust),
+      distinctUntilChanged()
+    )
 
   /* Combine into a single hot observable */
-  return combineLatest(top$, height$, active$).pipe(
-    map(([offset, height, active]) => ({ offset, height, active })),
-    shareReplay({ bufferSize: 1, refCount: true })
-  )
+  return combineLatest(height$, active$)
+    .pipe(
+      map(([height, active]) => ({
+        offset: container.offsetTop - adjust,
+        height,
+        active
+      })),
+      shareReplay(1)
+    )
 }
diff --git a/src/assets/javascripts/component/sidebar/index.ts b/src/assets/javascripts/component/sidebar/index.ts
index e46b5411a..1e86cf610 100644
--- a/src/assets/javascripts/component/sidebar/index.ts
+++ b/src/assets/javascripts/component/sidebar/index.ts
@@ -20,16 +20,10 @@
  * IN THE SOFTWARE.
  */
 
-import { Observable } from "rxjs"
-import {
-  filter,
-  finalize,
-  map,
-  shareReplay,
-  switchMap,
-  takeUntil
-} from "rxjs/operators"
+import { Observable, combineLatest } from "rxjs"
+import { map, shareReplay } from "rxjs/operators"
 
+import { ViewportOffset } from "../../ui"
 import { Container } from "../container"
 
 /* ----------------------------------------------------------------------------
@@ -53,7 +47,7 @@ export interface Sidebar {
  */
 interface Options {
   container$: Observable<Container>    /* Container state observable */
-  toggle$: Observable<boolean>         /* Toggle observable */
+  offset$: Observable<ViewportOffset>  /* Viewport offset observable */
 }
 
 /* ----------------------------------------------------------------------------
@@ -111,32 +105,34 @@ export function unsetSidebarLock(sidebar: HTMLElement): void {
  * @return Sidebar state observable
  */
 export function fromSidebar(
-  sidebar: HTMLElement, { container$, toggle$ }: Options
+  sidebar: HTMLElement, { container$, offset$ }: Options
 ): Observable<Sidebar> {
-  const sidebar$ = toggle$.pipe(
-    filter(toggle => toggle === true),
-    switchMap(() => container$.pipe(
-      finalize(() => {
-        unsetSidebarHeight(sidebar)
-        unsetSidebarLock(sidebar)
-      }),
-      takeUntil(toggle$.pipe(
-        filter(toggle => toggle === false)
-      ))
-    )),
-    map<Container, Sidebar>(({ height, active }) => ({
-      height,
-      lock: active
-    })),
-    shareReplay({ bufferSize: 1, refCount: true })
+
+  /* Adjust for internal container offset */
+  const adjust = parseFloat(
+    getComputedStyle(sidebar.parentElement!)
+      .getPropertyValue("padding-top")
   )
 
-  /* Subscribe sidebar element */
-  sidebar$.subscribe(({ height, lock }) => {
-    setSidebarHeight(sidebar, height)
-    setSidebarLock(sidebar, lock)
-  })
+  /* Compute the sidebars's available height */
+  const height$ = combineLatest(offset$, container$)
+    .pipe(
+      map(([{ y }, { offset, height }]) => {
+        return height - adjust
+          + Math.min(adjust, Math.max(0, y - offset))
+      })
+    )
 
-  /* Return observable */
-  return sidebar$
+  /* Compute whether the sidebar should be locked */
+  const lock$ = combineLatest(offset$, container$)
+    .pipe(
+      map(([{ y }, { offset }]) => y >= offset + adjust)
+    )
+
+  /* Combine into single hot observable */
+  return combineLatest(height$, lock$)
+    .pipe(
+      map(([height, lock]) => ({ height, lock })),
+      shareReplay(1)
+    )
 }
diff --git a/src/assets/javascripts/index.ts b/src/assets/javascripts/index.ts
index 82579f40b..94c4847b6 100644
--- a/src/assets/javascripts/index.ts
+++ b/src/assets/javascripts/index.ts
@@ -20,15 +20,23 @@
  * IN THE SOFTWARE.
  */
 
+import { animationFrameScheduler, interval, of } from "rxjs"
+import { concatMap, concatMapTo, filter, finalize, mapTo, mergeMap, skipUntil, startWith, switchMap, takeUntil, tap, throttleTime, windowToggle } from "rxjs/operators"
 import {
   fromContainer,
-  fromSidebar
+  fromSidebar,
+  setSidebarHeight,
+  setSidebarLock,
+  unsetSidebarHeight,
+  unsetSidebarLock,
+  withToggle
 } from "./component"
 import {
   fromMediaQuery,
   fromViewportOffset,
   fromViewportSize,
   getElement,
+  withMediaQuery,
 } from "./ui"
 
 // ----------------------------------------------------------------------------
@@ -57,12 +65,49 @@ const container$ = fromContainer(container, header, { size$, offset$ })
 // ---
 
 const nav = getElement("[data-md-component=navigation")!
-const nav$ = fromSidebar(nav, { container$, toggle$: screenAndAbove$ })
+
+fromSidebar(nav, { container$, offset$ })
+  .pipe(
+    withMediaQuery(screenAndAbove$),
+    concatMap(sidebar$ => sidebar$.pipe(
+      finalize(() => {
+        unsetSidebarHeight(nav)
+        unsetSidebarLock(nav)
+      })
+    ))
+  )
+    .subscribe(({ height, lock }) => {
+      setSidebarHeight(nav, height)
+      setSidebarLock(nav, lock)
+    })
 
 const toc = getElement("[data-md-component=toc")!
-const toc$ = fromSidebar(toc, { container$, toggle$: tabletAndAbove$ })
+
+fromSidebar(toc, { container$, offset$ })
+  .pipe(
+    withMediaQuery(tabletAndAbove$),
+    concatMap(sidebar$ => sidebar$.pipe(
+      finalize(() => {
+        unsetSidebarHeight(toc)
+        unsetSidebarLock(toc)
+      })
+    ))
+  )
+    .subscribe(({ height, lock }) => {
+      setSidebarHeight(toc, height)
+      setSidebarLock(toc, lock)
+    })
 
 // ----------------------------------------------------------------------------
 
 export function app(config: any) {
+  // TODO:
+  let parent = container.parentElement as HTMLElement
+  const height = 0
+
+  // TODO: write a fromHeader (?) component observable which
+  // this fromHeader should take the container and ...?
+  // container$.subscribe()
+
+  // container padding = "with parent" + 30px (padding of container...)
 }
diff --git a/src/assets/javascripts/ui/location/index.ts b/src/assets/javascripts/ui/location/index.ts
index f0690f2c1..28706823c 100644
--- a/src/assets/javascripts/ui/location/index.ts
+++ b/src/assets/javascripts/ui/location/index.ts
@@ -21,7 +21,7 @@
  */
 
 import { Observable, fromEvent } from "rxjs"
-import { filter, map, shareReplay, startWith } from "rxjs/operators"
+import { filter, map, share, startWith } from "rxjs/operators"
 
 /* ----------------------------------------------------------------------------
  * Data
@@ -42,10 +42,11 @@ const hash$ = fromEvent<HashChangeEvent>(window, "hashchange")
  * @return Location hash observable
  */
 export function fromLocationHash(): Observable<string> {
-  return hash$.pipe(
-    map(() => document.location.hash),
-    startWith(document.location.hash),
-    filter(hash => hash.length > 0),
-    shareReplay({ bufferSize: 1, refCount: true })
-  )
+  return hash$
+    .pipe(
+      map(() => document.location.hash),
+      startWith(document.location.hash),
+      filter(hash => hash.length > 0),
+      share()
+    )
 }
diff --git a/src/assets/javascripts/ui/viewport/_/index.ts b/src/assets/javascripts/ui/viewport/_/index.ts
index 2d3765e67..7cc2c8af4 100644
--- a/src/assets/javascripts/ui/viewport/_/index.ts
+++ b/src/assets/javascripts/ui/viewport/_/index.ts
@@ -93,11 +93,12 @@ export function getViewportSize(): ViewportSize {
  * @return Viewport offset observable
  */
 export function fromViewportOffset(): Observable<ViewportOffset> {
-  return merge(scroll$, resize$).pipe(
-    map(getViewportOffset),
-    startWith(getViewportOffset()),
-    shareReplay({ bufferSize: 1, refCount: true })
-  )
+  return merge(scroll$, resize$)
+    .pipe(
+      map(getViewportOffset),
+      startWith(getViewportOffset()),
+      shareReplay(1)
+    )
 }
 
 /**
@@ -106,9 +107,10 @@ export function fromViewportOffset(): Observable<ViewportOffset> {
  * @return Viewport size observable
  */
 export function fromViewportSize(): Observable<ViewportSize> {
-  return resize$.pipe(
-    map(getViewportSize),
-    startWith(getViewportSize()),
-    shareReplay({ bufferSize: 1, refCount: true })
-  )
+  return resize$
+    .pipe(
+      map(getViewportSize),
+      startWith(getViewportSize()),
+      shareReplay(1)
+    )
 }
diff --git a/src/assets/javascripts/ui/viewport/breakpoint/index.ts b/src/assets/javascripts/ui/viewport/breakpoint/index.ts
index 377ca7365..510dd09d1 100644
--- a/src/assets/javascripts/ui/viewport/breakpoint/index.ts
+++ b/src/assets/javascripts/ui/viewport/breakpoint/index.ts
@@ -20,8 +20,17 @@
  * IN THE SOFTWARE.
  */
 
-import { Observable, fromEventPattern } from "rxjs"
-import { shareReplay, startWith } from "rxjs/operators"
+import {
+  Observable,
+  OperatorFunction,
+  fromEventPattern
+} from "rxjs"
+import {
+  filter,
+  shareReplay,
+  startWith,
+  windowToggle
+} from "rxjs/operators"
 
 /* ----------------------------------------------------------------------------
  * Functions
@@ -38,8 +47,26 @@ export function fromMediaQuery(query: string): Observable<boolean> {
   const media = window.matchMedia(query)
   return fromEventPattern<boolean>(next =>
     media.addListener(() => next(media.matches))
-  ).pipe(
-    startWith(media.matches),
-    shareReplay({ bufferSize: 1, refCount: true })
   )
+    .pipe(
+      startWith(media.matches),
+      shareReplay(1)
+    )
+}
+
+/**
+ * Only emit values from the source observable when a media query matches
+ *
+ * @template T - Observable value type
+ *
+ * @param query - Media query observable
+ *
+ * @return Observable of source observable values
+ */
+export function withMediaQuery<T>(
+  query$: Observable<boolean>
+): OperatorFunction<T, Observable<T>> {
+  const start$ = query$.pipe(filter(match => match === true))
+  const until$ = query$.pipe(filter(match => match === false))
+  return windowToggle<T, boolean>(start$, () => until$)
 }