diff --git a/ui/src/App.vue b/ui/src/App.vue
index 0f7a739..dccb68f 100644
--- a/ui/src/App.vue
+++ b/ui/src/App.vue
@@ -7,7 +7,18 @@
   </section>
 
   <section class="section px-3">
-    <div class="container">
+    <progress
+      v-if="store.background_image === 'loading'"
+      class="progress is-primary"
+      max="100"
+    />
+    <div
+      v-else-if="store.background_image === 'error'"
+      class="notification is-danger"
+    >
+      Hintergrundbild konnte nicht geladen werden
+    </div>
+    <div v-else class="container">
       <AdminView v-if="store.is_admin" />
       <UserView v-else />
     </div>
diff --git a/ui/src/components/AdminButton.vue b/ui/src/components/AdminButton.vue
index 4defc89..75ab479 100644
--- a/ui/src/components/AdminButton.vue
+++ b/ui/src/components/AdminButton.vue
@@ -15,6 +15,7 @@ import { Credentials } from "@/lib/model";
 import { advent22Store } from "@/lib/store";
 import { Options, Vue } from "vue-class-component";
 
+import { APIError } from "@/lib/api_error";
 import BulmaButton from "./bulma/Button.vue";
 import LoginModal from "./LoginModal.vue";
 
@@ -44,7 +45,7 @@ export default class extends Vue {
 
     this.store
       .login(creds)
-      .catch(this.store.alert_user_error)
+      .catch((error) => APIError.alert(error))
       .finally(() => (this.is_busy = false));
   }
 
diff --git a/ui/src/components/Calendar.vue b/ui/src/components/Calendar.vue
index dcb5860..6ecf4e9 100644
--- a/ui/src/components/Calendar.vue
+++ b/ui/src/components/Calendar.vue
@@ -29,14 +29,14 @@
 
   <figure>
     <div class="image is-unselectable">
-      <img :src="store.background_image" />
+      <img :src="_ensure_loaded(store.background_image).data_url" />
       <ThouCanvas>
         <CalendarDoor
           v-for="(door, index) in doors"
           :key="`door-${index}`"
           :door="door"
           :visible="store.is_touch_device"
-          :title="$advent22.name_door(door.day)"
+          :title="_name_door(door.day)"
           @click="door_click(door.day)"
           style="cursor: pointer"
         />
@@ -46,6 +46,10 @@
 </template>
 
 <script lang="ts">
+import { API } from "@/lib/api";
+import { APIError } from "@/lib/api_error";
+import { ensure_loaded, Loading, name_door } from "@/lib/helpers";
+import { ImageData } from "@/lib/model";
 import { Door } from "@/lib/rects/door";
 import { advent22Store } from "@/lib/store";
 import { Options, Vue } from "vue-class-component";
@@ -96,26 +100,32 @@ export default class extends Vue {
     });
   }
 
-  public door_click(day: number) {
+  public async door_click(day: number) {
     if (this.toast_timeout !== undefined) clearTimeout(this.toast_timeout);
     this.toast?.hide();
 
     if (this.multi_modal === undefined) return;
     this.multi_modal.show_progress();
 
-    this.$advent22
-      .api_get_blob(`user/image_${day}`)
-      .then((image_src) => {
-        this.multi_modal!.show_image(image_src, this.$advent22.name_door(day));
-      })
-      .catch((error) => {
-        this.store.alert_user_error(error);
-        this.multi_modal!.hide();
-      });
+    try {
+      const day_image = await API.request<ImageData>(`user/image_${day}`);
+      this.multi_modal!.show_image(day_image.data_url, name_door(day));
+    } catch (error) {
+      APIError.alert(error);
+      this.multi_modal!.hide();
+    }
   }
 
   public beforeUnmount(): void {
     this.toast?.hide();
   }
+
+  public _ensure_loaded<T>(o: Loading<T>): T {
+    return ensure_loaded(o);
+  }
+
+  public _name_door(day: number): string {
+    return name_door(day);
+  }
 }
 </script>
diff --git a/ui/src/components/UserView.vue b/ui/src/components/UserView.vue
index 90a431b..7aab8df 100644
--- a/ui/src/components/UserView.vue
+++ b/ui/src/components/UserView.vue
@@ -1,25 +1,22 @@
 <template>
-  <template v-if="store.is_initialized === true">
-    <Calendar :doors="store.user_doors" />
-    <hr />
-    <div class="content" v-html="store.site_config.content" />
-    <div class="content has-text-primary">
-      <template v-if="store.next_door_target === null">
-        Alle {{ store.user_doors.length }} Türchen offen!
+  <Calendar :doors="store.user_doors" />
+  <hr />
+  <div class="content" v-html="store.site_config.content" />
+  <div class="content has-text-primary">
+    <template v-if="store.next_door_target === null">
+      Alle {{ store.user_doors.length }} Türchen offen!
+    </template>
+    <template v-else>
+      <template v-if="store.user_doors.length === 0">
+        Zeit bis zum ersten Türchen:
       </template>
       <template v-else>
-        <template v-if="store.user_doors.length === 0">
-          Zeit bis zum ersten Türchen:
-        </template>
-        <template v-else>
-          {{ store.user_doors.length }} Türchen offen. Zeit bis zum nächsten
-          Türchen:
-        </template>
-        <CountDown :until="store.next_door_target" />
+        {{ store.user_doors.length }} Türchen offen. Zeit bis zum nächsten
+        Türchen:
       </template>
-    </div>
-  </template>
-  <progress v-else class="progress is-primary" max="100" />
+      <CountDown :until="store.next_door_target" />
+    </template>
+  </div>
 </template>
 
 <script lang="ts">
diff --git a/ui/src/components/admin/CalendarAssistant.vue b/ui/src/components/admin/CalendarAssistant.vue
index 0af5059..2bf9297 100644
--- a/ui/src/components/admin/CalendarAssistant.vue
+++ b/ui/src/components/admin/CalendarAssistant.vue
@@ -46,8 +46,9 @@
 </template>
 
 <script lang="ts">
-import { objForEach } from "@/lib/helpers";
-import { NumStrDict } from "@/lib/model";
+import { API } from "@/lib/api";
+import { name_door, objForEach } from "@/lib/helpers";
+import { ImageData, NumStrDict } from "@/lib/model";
 import { Options, Vue } from "vue-class-component";
 
 import MultiModal from "../MultiModal.vue";
@@ -77,8 +78,8 @@ export default class extends Vue {
 
   public on_open(ready: () => void, fail: () => void): void {
     Promise.all([
-      this.$advent22.api_get<NumStrDict>("admin/day_parts"),
-      this.$advent22.api_get<NumStrDict>("admin/day_image_names"),
+      API.request<NumStrDict>("admin/day_parts"),
+      API.request<NumStrDict>("admin/day_image_names"),
     ])
       .then(([day_parts, day_image_names]) => {
         const _ensure_day_in_data = (day: number) => {
@@ -102,16 +103,16 @@ export default class extends Vue {
       .catch(fail);
   }
 
-  public door_click(day: number) {
+  public async door_click(day: number) {
     if (this.multi_modal === undefined) return;
     this.multi_modal.show_progress();
 
-    this.$advent22
-      .api_get_blob(`user/image_${day}`)
-      .then((image_src) =>
-        this.multi_modal!.show_image(image_src, this.$advent22.name_door(day)),
-      )
-      .catch(() => this.multi_modal!.hide());
+    try {
+      const day_image = await API.request<ImageData>(`user/image_${day}`);
+      this.multi_modal!.show_image(day_image.data_url, name_door(day));
+    } catch (error) {
+      this.multi_modal!.hide();
+    }
   }
 }
 </script>
diff --git a/ui/src/components/admin/ConfigView.vue b/ui/src/components/admin/ConfigView.vue
index bc99ef9..305e993 100644
--- a/ui/src/components/admin/ConfigView.vue
+++ b/ui/src/components/admin/ConfigView.vue
@@ -189,6 +189,7 @@ import { advent22Store } from "@/lib/store";
 import { DateTime } from "luxon";
 import { Options, Vue } from "vue-class-component";
 
+import { API } from "@/lib/api";
 import BulmaDrawer from "../bulma/Drawer.vue";
 import BulmaSecret from "../bulma/Secret.vue";
 import CountDown from "../CountDown.vue";
@@ -256,8 +257,8 @@ export default class extends Vue {
   public on_open(ready: () => void, fail: () => void): void {
     Promise.all([
       this.store.update(),
-      this.$advent22.api_get<AdminConfigModel>("admin/config_model"),
-      this.$advent22.api_get<DoorSaved[]>("admin/doors"),
+      API.request<AdminConfigModel>("admin/config_model"),
+      API.request<DoorSaved[]>("admin/doors"),
     ])
       .then(([store_update, admin_config_model, doors]) => {
         store_update; // discard value
@@ -271,15 +272,13 @@ export default class extends Vue {
   }
 
   public load_dav_credentials(): void {
-    this.$advent22
-      .api_get<Credentials>("admin/dav_credentials")
+    API.request<Credentials>("admin/dav_credentials")
       .then((creds) => (this.dav_credentials = creds))
       .catch(() => {});
   }
 
   public load_ui_credentials(): void {
-    this.$advent22
-      .api_get<Credentials>("admin/ui_credentials")
+    API.request<Credentials>("admin/ui_credentials")
       .then((creds) => (this.ui_credentials = creds))
       .catch(() => {});
   }
diff --git a/ui/src/components/admin/DoorMapEditor.vue b/ui/src/components/admin/DoorMapEditor.vue
index 30ccea9..14ee36d 100644
--- a/ui/src/components/admin/DoorMapEditor.vue
+++ b/ui/src/components/admin/DoorMapEditor.vue
@@ -74,6 +74,8 @@ import { Door } from "@/lib/rects/door";
 import { advent22Store } from "@/lib/store";
 import { Options, Vue } from "vue-class-component";
 
+import { API } from "@/lib/api";
+import { APIError } from "@/lib/api_error";
 import { toast } from "bulma-toast";
 import Calendar from "../Calendar.vue";
 import BulmaBreadcrumbs, { Step } from "../bulma/Breadcrumbs.vue";
@@ -107,8 +109,7 @@ export default class extends Vue {
 
   private load_doors(): Promise<void> {
     return new Promise<void>((resolve, reject) => {
-      this.$advent22
-        .api_get<DoorSaved[]>("admin/doors")
+      API.request<DoorSaved[]>("admin/doors")
         .then((data) => {
           this.doors.length = 0;
 
@@ -119,7 +120,7 @@ export default class extends Vue {
           resolve();
         })
         .catch((error) => {
-          this.store.alert_user_error(error);
+          APIError.alert(error);
           reject();
         });
     });
@@ -133,11 +134,10 @@ export default class extends Vue {
         data.push(door.save());
       }
 
-      this.$advent22
-        .api_put("admin/doors", data)
+      API.request<void>({ endpoint: "admin/doors", method: "PUT", data: data })
         .then(resolve)
         .catch((error) => {
-          this.store.alert_user_error(error);
+          APIError.alert(error);
           reject();
         });
     });
diff --git a/ui/src/components/calendar/SVGRect.vue b/ui/src/components/calendar/SVGRect.vue
index a76825d..102ff48 100644
--- a/ui/src/components/calendar/SVGRect.vue
+++ b/ui/src/components/calendar/SVGRect.vue
@@ -1,10 +1,10 @@
 <template>
   <foreignObject
-    :x="Math.round(store.calendar_aspect_ratio * rectangle.left)"
+    :x="Math.round(aspect_ratio * rectangle.left)"
     :y="rectangle.top"
-    :width="Math.round(store.calendar_aspect_ratio * rectangle.width)"
+    :width="Math.round(aspect_ratio * rectangle.width)"
     :height="rectangle.height"
-    :style="`transform: scaleX(${1 / store.calendar_aspect_ratio})`"
+    :style="`transform: scaleX(${1 / aspect_ratio})`"
   >
     <div
       xmlns="http://www.w3.org/1999/xhtml"
@@ -18,6 +18,7 @@
 </template>
 
 <script lang="ts">
+import { loading_success } from "@/lib/helpers";
 import { Rectangle } from "@/lib/rects/rectangle";
 import { advent22Store } from "@/lib/store";
 import { Options, Vue } from "vue-class-component";
@@ -59,6 +60,14 @@ export default class extends Vue {
 
     return result;
   }
+
+  public get aspect_ratio(): number {
+    if (!loading_success(this.store.background_image)) return 1;
+
+    return (
+      this.store.background_image.height / this.store.background_image.width
+    );
+  }
 }
 </script>
 
diff --git a/ui/src/components/calendar/ThouCanvas.vue b/ui/src/components/calendar/ThouCanvas.vue
index 0df5c33..d2cd752 100644
--- a/ui/src/components/calendar/ThouCanvas.vue
+++ b/ui/src/components/calendar/ThouCanvas.vue
@@ -57,15 +57,6 @@ function mouse_event_validator(event: object, point: object): boolean {
 export default class extends Vue {
   public readonly store = advent22Store();
 
-  public mounted(): void {
-    new ResizeObserver(([first, ...rest]) => {
-      if (rest.length > 0)
-        console.warn(`Unexpected ${rest.length} extra entries!`);
-
-      this.store.set_calendar_aspect_ratio(first.contentRect);
-    }).observe(this.$el);
-  }
-
   public transform_mouse_event(event: MouseEvent) {
     const point = get_event_thous(event);
     this.$emit(event.type, event, point);
diff --git a/ui/src/components/editor/DoorChooser.vue b/ui/src/components/editor/DoorChooser.vue
index 6d4b39a..87cd403 100644
--- a/ui/src/components/editor/DoorChooser.vue
+++ b/ui/src/components/editor/DoorChooser.vue
@@ -11,7 +11,7 @@
       </ul>
     </div>
     <figure class="image is-unselectable">
-      <img :src="store.background_image" />
+      <img :src="_ensure_loaded(store.background_image).data_url" />
       <ThouCanvas>
         <PreviewDoor
           v-for="(door, index) in doors"
@@ -24,6 +24,7 @@
 </template>
 
 <script lang="ts">
+import { ensure_loaded, Loading } from "@/lib/helpers";
 import { Door } from "@/lib/rects/door";
 import { advent22Store } from "@/lib/store";
 import { Options, Vue } from "vue-class-component";
@@ -43,5 +44,9 @@ import PreviewDoor from "./PreviewDoor.vue";
 export default class extends Vue {
   public doors!: Door[];
   public readonly store = advent22Store();
+
+  public _ensure_loaded<T>(o: Loading<T>): T {
+    return ensure_loaded(o);
+  }
 }
 </script>
diff --git a/ui/src/components/editor/DoorPlacer.vue b/ui/src/components/editor/DoorPlacer.vue
index 951b0f8..efce3c0 100644
--- a/ui/src/components/editor/DoorPlacer.vue
+++ b/ui/src/components/editor/DoorPlacer.vue
@@ -9,13 +9,14 @@
       </ul>
     </div>
     <figure class="image is-unselectable">
-      <img :src="store.background_image" />
+      <img :src="_ensure_loaded(store.background_image).data_url" />
       <DoorCanvas :doors="doors" />
     </figure>
   </div>
 </template>
 
 <script lang="ts">
+import { ensure_loaded, Loading } from "@/lib/helpers";
 import { Door } from "@/lib/rects/door";
 import { advent22Store } from "@/lib/store";
 import { Options, Vue } from "vue-class-component";
@@ -33,5 +34,9 @@ import DoorCanvas from "./DoorCanvas.vue";
 export default class extends Vue {
   public doors!: Door[];
   public readonly store = advent22Store();
+
+  public _ensure_loaded<T>(o: Loading<T>): T {
+    return ensure_loaded(o);
+  }
 }
 </script>
diff --git a/ui/src/lib/api_error.ts b/ui/src/lib/api_error.ts
index 6e94f59..46deaad 100644
--- a/ui/src/lib/api_error.ts
+++ b/ui/src/lib/api_error.ts
@@ -70,4 +70,8 @@ export class APIError extends Error {
       type: "is-danger",
     });
   }
+
+  public static alert(error: unknown) {
+    new APIError(error, "").alert();
+  }
 }
diff --git a/ui/src/lib/helpers.ts b/ui/src/lib/helpers.ts
index d9987a0..74ef4e7 100644
--- a/ui/src/lib/helpers.ts
+++ b/ui/src/lib/helpers.ts
@@ -20,6 +20,12 @@ export function loading_success<T>(o: Loading<T>): o is T {
   return true;
 }
 
+export function ensure_loaded<T>(o: Loading<T>): T {
+  if (!loading_success(o)) throw "";
+
+  return o;
+}
+
 export function handle_error(error: unknown) {
   if (error instanceof APIError) {
     error.alert();
@@ -27,3 +33,7 @@ export function handle_error(error: unknown) {
     console.error(error);
   }
 }
+
+export function name_door(day: number): string {
+  return `Türchen ${day}`;
+}
diff --git a/ui/src/main.ts b/ui/src/main.ts
index 4bb7bdb..89115e0 100644
--- a/ui/src/main.ts
+++ b/ui/src/main.ts
@@ -1,5 +1,4 @@
 import { advent22Store } from "@/lib/store";
-import { Advent22Plugin } from "@/plugins/advent22";
 import { FontAwesomePlugin } from "@/plugins/fontawesome";
 import * as bulmaToast from "bulma-toast";
 import { createPinia } from "pinia";
@@ -10,10 +9,9 @@ import "@/main.scss";
 
 const app = createApp(App);
 
-app.use(Advent22Plugin);
 app.use(FontAwesomePlugin);
-
 app.use(createPinia());
+
 advent22Store().init();
 
 app.mount("#app");