diff --git a/.github/workflows/docker-publish.yml b/.github/workflows/docker-publish.yml
index d90a0be..2270b22 100644
--- a/.github/workflows/docker-publish.yml
+++ b/.github/workflows/docker-publish.yml
@@ -3,8 +3,8 @@ name: Publish Docker Image
 on:
   push:
     branches: [ "master" ]
-    # You can also trigger this on release tags:
-    # tags: [ 'v*.*.*' ]
+  # Uncomment to also trigger on release tags:
+  # tags: [ 'v*.*.*' ]
 
 env:
   REGISTRY_GHCR: ghcr.io
@@ -23,6 +23,9 @@ jobs:
         with:
           submodules: recursive
 
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Log in to GitHub Container Registry (GHCR)
         uses: docker/login-action@v3
         with:
@@ -36,9 +39,6 @@ jobs:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
-      - name: Setup Docker Buildx
-        uses: docker/setup-buildx-action@v3
-
       - name: Extract metadata (tags, labels) for Docker
         id: meta
         uses: docker/metadata-action@v5
@@ -48,10 +48,12 @@ jobs:
             docker.io/${{ secrets.DOCKERHUB_USERNAME }}/velxio
 
       - name: Build and push Docker image
-        uses: docker/build-push-action@v5
+        uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile.standalone
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
diff --git a/Dockerfile.standalone b/Dockerfile.standalone
index 882bba6..b251fe4 100644
--- a/Dockerfile.standalone
+++ b/Dockerfile.standalone
@@ -1,9 +1,9 @@
 # ---- Stage 1: Build frontend and wokwi-libs ----
-FROM node:20 AS frontend-builder
+FROM node:20-slim AS frontend-builder
 
 WORKDIR /app
 
-# Copy package.json for metadata generation and common dependencies
+# Copy root package.json (metadata/scripts)
 COPY package.json .
 RUN npm install
 
@@ -22,35 +22,34 @@ COPY wokwi-libs/wokwi-elements/ wokwi-libs/wokwi-elements/
 WORKDIR /app/wokwi-libs/wokwi-elements
 RUN npm install && npm run build
 
-# Build frontend and generate metadata
+# Build frontend
 WORKDIR /app
 COPY frontend/ frontend/
 COPY scripts/ scripts/
 WORKDIR /app/frontend
-# Explicitly install frontend dependencies
-RUN npm install
-# Now run the build which includes metadata generation
-RUN npm run build
+RUN npm install && npm run build
 
 
 # ---- Stage 2: Final Production Image ----
 FROM python:3.12-slim
 
-# Install system dependencies, arduino-cli, and nginx
+# Install system dependencies and nginx
 RUN apt-get update && apt-get install -y --no-install-recommends \
     curl \
     ca-certificates \
     nginx \
-    && curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh \
-    && mv bin/arduino-cli /usr/local/bin/ \
-    && rm -rf bin \
-    && apt-get purge -y curl \
-    && apt-get autoremove -y \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
-# Initialize arduino-cli and install AVR & RP2040 cores
-RUN arduino-cli core update-index \
+# Install arduino-cli into /usr/local/bin directly (avoids touching /bin)
+RUN curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh \
+    | BINDIR=/usr/local/bin sh
+
+# Initialize arduino-cli config, add RP2040 board manager URL, then install cores
+RUN arduino-cli config init \
+    && arduino-cli config add board_manager.additional_urls \
+       https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json \
+    && arduino-cli core update-index \
     && arduino-cli core install arduino:avr \
     && arduino-cli core install rp2040:rp2040
 
@@ -73,7 +72,6 @@ COPY --from=frontend-builder /app/frontend/dist /usr/share/nginx/html
 COPY deploy/entrypoint.sh /app/entrypoint.sh
 RUN chmod +x /app/entrypoint.sh
 
-# Expose port 80 for the unified web server
 EXPOSE 80
 
 CMD ["/app/entrypoint.sh"]
diff --git a/frontend/src/App.css b/frontend/src/App.css
index 0cc1cf6..c618b52 100644
--- a/frontend/src/App.css
+++ b/frontend/src/App.css
@@ -108,6 +108,22 @@ body {
   color: #ccc;
 }
 
+/* Resize handle for the file explorer sidebar */
+.explorer-resize-handle {
+  width: 4px;
+  flex-shrink: 0;
+  cursor: col-resize;
+  background: #2a2a2a;
+  transition: background 0.15s;
+  position: relative;
+  z-index: 5;
+}
+
+.explorer-resize-handle:hover,
+.explorer-resize-handle:active {
+  background: #007acc;
+}
+
 .editor-wrapper {
   flex: 1;
   overflow: hidden;
diff --git a/frontend/src/components/editor/FileExplorer.css b/frontend/src/components/editor/FileExplorer.css
index 312a95f..14b7756 100644
--- a/frontend/src/components/editor/FileExplorer.css
+++ b/frontend/src/components/editor/FileExplorer.css
@@ -1,6 +1,5 @@
 .file-explorer {
-  width: 195px;
-  flex-shrink: 0;
+  width: 100%;
   background: #252526;
   border-right: 1px solid #333;
   display: flex;
diff --git a/frontend/src/pages/EditorPage.tsx b/frontend/src/pages/EditorPage.tsx
index 3b16155..9060305 100644
--- a/frontend/src/pages/EditorPage.tsx
+++ b/frontend/src/pages/EditorPage.tsx
@@ -22,6 +22,10 @@ const BOTTOM_PANEL_MIN = 80;
 const BOTTOM_PANEL_MAX = 600;
 const BOTTOM_PANEL_DEFAULT = 200;
 
+const EXPLORER_MIN = 120;
+const EXPLORER_MAX = 500;
+const EXPLORER_DEFAULT = 210;
+
 const resizeHandleStyle: React.CSSProperties = {
   height: 5,
   flexShrink: 0,
@@ -42,6 +46,7 @@ export const EditorPage: React.FC = () => {
   const [saveModalOpen, setSaveModalOpen] = useState(false);
   const [loginPromptOpen, setLoginPromptOpen] = useState(false);
   const [explorerOpen, setExplorerOpen] = useState(true);
+  const [explorerWidth, setExplorerWidth] = useState(EXPLORER_DEFAULT);
   const user = useAuthStore((s) => s.user);
 
   const handleSaveClick = useCallback(() => {
@@ -110,6 +115,27 @@ export const EditorPage: React.FC = () => {
     document.addEventListener('mouseup', onUp);
   }, [bottomPanelHeight]);
 
+  const handleExplorerResizeMouseDown = useCallback((e: React.MouseEvent) => {
+    e.preventDefault();
+    const startX = e.clientX;
+    const startWidth = explorerWidth;
+
+    const onMove = (ev: MouseEvent) => {
+      const delta = ev.clientX - startX;
+      setExplorerWidth(Math.max(EXPLORER_MIN, Math.min(EXPLORER_MAX, startWidth + delta)));
+    };
+    const onUp = () => {
+      document.body.style.cursor = '';
+      document.body.style.userSelect = '';
+      document.removeEventListener('mousemove', onMove);
+      document.removeEventListener('mouseup', onUp);
+    };
+    document.body.style.cursor = 'col-resize';
+    document.body.style.userSelect = 'none';
+    document.addEventListener('mousemove', onMove);
+    document.addEventListener('mouseup', onUp);
+  }, [explorerWidth]);
+
   return (
     <div className="app">
       <AppHeader />
@@ -120,8 +146,15 @@ export const EditorPage: React.FC = () => {
           className="editor-panel"
           style={{ width: `${editorWidthPct}%`, display: 'flex', flexDirection: 'row' }}
         >
-          {/* File explorer sidebar */}
-          {explorerOpen && <FileExplorer onSaveClick={handleSaveClick} />}
+          {/* File explorer sidebar + resize handle */}
+          {explorerOpen && (
+            <>
+              <div style={{ width: explorerWidth, flexShrink: 0, display: 'flex', overflow: 'hidden' }}>
+                <FileExplorer onSaveClick={handleSaveClick} />
+              </div>
+              <div className="explorer-resize-handle" onMouseDown={handleExplorerResizeMouseDown} />
+            </>
+          )}
 
           {/* Editor main area */}
           <div style={{ flex: 1, display: 'flex', flexDirection: 'column', overflow: 'hidden', minWidth: 0 }}>