diff --git a/public/fonts/InterVariable.woff2 b/public/fonts/InterVariable.woff2
new file mode 100644
index 0000000..22a12b0
Binary files /dev/null and b/public/fonts/InterVariable.woff2 differ
diff --git a/src/index.tsx b/src/index.tsx
index 166f7f4..0af1d28 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -61,7 +61,7 @@ window.addEventListener('load', async () => {
   
   registerCustomAppHeightCSSProperty();
 
-  const fs = await createEditorFS({prefix: '/', allowPersistence: isInStandaloneMode});
+  const fs = await createEditorFS({prefix: '/libraries/', allowPersistence: isInStandaloneMode});
 
   await registerOpenSCADLanguage(fs, '/', zipArchives);
 
diff --git a/src/runner/openscad-worker.ts b/src/runner/openscad-worker.ts
index cdaae72..aba0d6d 100644
--- a/src/runner/openscad-worker.ts
+++ b/src/runner/openscad-worker.ts
@@ -93,6 +93,11 @@ addEventListener('message', async (e) => {
     if (inputs) {
       for (const source of inputs) {
         try {
+          if (source.path.startsWith('/libraries/')) {  
+            console.log(`Skipping ${source.path}`);
+            continue;
+          }
+          console.log(`Writing ${source.path}`);
           instance.FS.writeFile(source.path, await fetchSource(source));
         } catch (e) {
           console.trace(e);
diff --git a/src/state/fragment-state.ts b/src/state/fragment-state.ts
index 03227c2..9e87631 100644
--- a/src/state/fragment-state.ts
+++ b/src/state/fragment-state.ts
@@ -57,6 +57,10 @@ export async function readStateFromFragment(): Promise<State | null> {
         // For testing
         const src = decodeURIComponent(serialized.substring('src:'.length));
         return createInitialState(null, src);
+      } else if (serialized.startsWith('testpath:')) {
+        // For testing
+        const path = decodeURIComponent(serialized.substring('testpath:'.length));
+        return createInitialState(null, '...', path);
       }
       let obj;
       try {
diff --git a/src/state/initial-state.ts b/src/state/initial-state.ts
index 66d7170..26cd638 100644
--- a/src/state/initial-state.ts
+++ b/src/state/initial-state.ts
@@ -6,7 +6,7 @@ import { State } from './app-state';
 export const defaultSourcePath = '/playground.scad';
 export const defaultModelColor = '#f9d72c';
   
-export function createInitialState(state: State | null, content: string = defaultScad): State {
+export function createInitialState(state: State | null, content = defaultScad, activePath = defaultSourcePath): State {
 
   type Mode = State['view']['layout']['mode'];
   const mode: Mode = window.matchMedia("(min-width: 768px)").matches 
@@ -14,8 +14,8 @@ export function createInitialState(state: State | null, content: string = defaul
 
   const initialState: State = {
     params: {
-      activePath: defaultSourcePath,
-      sources: [{path: defaultSourcePath, content}],
+      activePath: activePath,
+      sources: [{path: activePath, content}],
       features: [],
       exportFormat2D: 'svg',
       exportFormat3D: 'glb',
diff --git a/src/state/model.ts b/src/state/model.ts
index 7ea8ce5..85dbaeb 100644
--- a/src/state/model.ts
+++ b/src/state/model.ts
@@ -118,17 +118,24 @@ export class Model {
   }
 
   openFile(path: string) {
-    // alert(`TODO: open ${path}`);
+    // console.log(`openFile: ${path}`);
     if (this.mutate(s => {
       if (s.params.activePath != path) {
-        s.params.activePath = path;
-        if (!s.params.sources.find(src => src.path === path)) {
-          let content = '';
+        const readSource = (path: string) => {
           try {
-            content = new TextDecoder("utf-8").decode(this.fs.readFileSync(path));
+            return new TextDecoder("utf-8").decode(this.fs.readFileSync(path));
           } catch (e) {
             console.error('Error while reading file:', e);
+            return '';
           }
+        };
+        // Remove source of previous active path if it's unmodified
+        const activePathContent = readSource(s.params.activePath);
+        s.params.sources = s.params.sources.filter(src => src.path !== s.params.activePath || src.content != activePathContent);
+
+        s.params.activePath = path;
+        if (!s.params.sources.find(src => src.path === path)) {
+          const content = readSource(path);
           s.params.sources = [...s.params.sources, {path, content}];
         }
         s.lastCheckerRun = undefined;
@@ -307,6 +314,7 @@ export class Model {
   }
 
   async render({isPreview, mountArchives, now, retryInOtherDim}: {isPreview: boolean, mountArchives?: boolean, now: boolean, retryInOtherDim?: boolean}) {
+    // console.log(JSON.stringify(this.state, null, 2));
     mountArchives ??= true;
     retryInOtherDim ??= true;
     const setRendering = (s: State, value: boolean) => {
diff --git a/tests/e2e.test.js b/tests/e2e.test.js
index 8f7ea65..de3eb94 100644
--- a/tests/e2e.test.js
+++ b/tests/e2e.test.js
@@ -21,7 +21,8 @@ beforeEach(async () => {
 
 afterEach(async () => {
   // console.log('Messages:', JSON.stringify(messages, null, 2));
-  console.log('Messages:', JSON.stringify(messages.map(({text}) => text), null, 2));
+  const testName = expect.getState().currentTestName;
+  console.log(`[${testName}] Messages:`, JSON.stringify(messages.map(({text}) => text), null, 2));
     
   const errors = messages.filter(msg =>
       msg.type === 'error' &&
@@ -34,6 +35,9 @@ afterEach(async () => {
 function loadSrc(src) {
   return page.goto(url + '#src:' + encodeURIComponent(src));
 }
+function loadPath(path) {
+  return page.goto(url + '#testpath:' + encodeURIComponent(path));
+}
 async function waitForViewer() {
   await page.waitForSelector('model-viewer');
   await page.waitForFunction(() => {
@@ -102,6 +106,12 @@ describe('e2e', () => {
     expect3DManifold();
   }, longTimeout);
 
+  test('load a demo by path', async () => {
+    await loadPath('/libraries/closepoints/demo_3D_art.scad');
+    await waitForViewer();
+    expect3DPolySet();
+  }, longTimeout);
+
   test('customizer & windows line endings work', async () => {
     await loadSrc([
       'myVar = 10;',