feat: default @block align to centerLeft

docs/guides/markdown-authoring.mdx

@@ -94,7 +94,7 @@ Use these properties on blocks. Sections support `flex` and `align`;
 `scrollable` applies to child blocks and widgets.
 
 - `flex` – Relative size (default: `1`). A column with `flex: 2` takes twice the space of `flex: 1`
-- `align` – Content alignment such as `topLeft`, `center`, and `bottomRight`
+- `align` – Content alignment such as `topLeft`, `center`, and `bottomRight` (default: `centerLeft`)
 - `scrollable` – Enable scrolling for overflow content (default: `false`)
 
 For complete value definitions, see the [Markdown syntax reference](../reference/markdown-syntax).

docs/reference/block-types.mdx

@@ -13,7 +13,7 @@ Content and widget blocks support these properties. Sections support `align`
 and `flex`, but scrolling is configured on child blocks or widgets.
 
 ### `align`
-**Type:** String | **Default:** `center`
+**Type:** String | **Default:** `centerLeft`
 
 Controls content alignment:
 - `topLeft`, `topCenter`, `topRight`

docs/reference/markdown-syntax.mdx

@@ -51,7 +51,7 @@ Built-in widgets (`image`, `dartpad`, `qrcode`) use the same widget syntax as `@
 ### `align`
 
 - Type: string
-- Default: `center`
+- Default: `centerLeft`
 - Values: `topLeft`, `topCenter`, `topRight`, `centerLeft`, `center`, `centerRight`, `bottomLeft`, `bottomCenter`, `bottomRight`
 
 ### `scrollable`

packages/superdeck/lib/src/rendering/blocks/block_widget.dart

@@ -62,9 +62,11 @@ class _BlockContainerState extends State<_BlockContainer> {
       child: content,
     );
 
-    // Apply alignment
+    // Apply alignment. Blocks default to centerLeft so prose and embedded
+    // widgets align with left-to-right reading flow; set `align: center` to
+    // restore centered placement explicitly.
     content = Align(
-      alignment: widget.block.align?.toAlignment ?? Alignment.center,
+      alignment: widget.block.align?.toAlignment ?? Alignment.centerLeft,
       child: content,
     );
 

packages/superdeck/test/src/behavior/alignment_behavior_test.dart

@@ -110,6 +110,42 @@ void main() {
       });
     });
 
+    group('default alignment', () {
+      testWidgets('ContentBlock without explicit align defaults to centerLeft', (
+        tester,
+      ) async {
+        final slide = Slide(
+          key: 'block-default-align',
+          sections: [
+            SectionBlock([ContentBlock('Hello')]),
+          ],
+        );
+        await SlideTestHarness.pumpSlide(tester, slide);
+
+        final alignWidget = tester.widget<Align>(find.byType(Align).first);
+        expect(alignWidget.alignment, Alignment.centerLeft);
+      });
+
+      testWidgets('WidgetBlock without explicit align defaults to centerLeft', (
+        tester,
+      ) async {
+        final slide = Slide(
+          key: 'widget-default-align',
+          sections: [
+            SectionBlock([WidgetBlock(name: 'plain')]),
+          ],
+        );
+        await SlideTestHarness.pumpSlide(
+          tester,
+          slide,
+          widgets: {'plain': (_) => const SizedBox.shrink()},
+        );
+
+        final alignWidget = tester.widget<Align>(find.byType(Align).first);
+        expect(alignWidget.alignment, Alignment.centerLeft);
+      });
+    });
+
     group('alignment in sections', () {
       testWidgets('different alignments per section', (tester) async {
         final slide = Slide(