add debug mode

lib/utils/offset_extensions.dart

@@ -10,4 +10,8 @@ extension OffsetCartesionOps on Offset {
   Offset operator -(Offset other) {
     return Offset(dx - other.dx, dy - other.dy);
   }
+
+  String coord() {
+    return '(${dx.toStringAsFixed(2)}, ${dy.toStringAsFixed(2)})';
+  }
 }

lib/utils/styles.dart

@@ -0,0 +1,8 @@
+import 'package:flutter/material.dart';
+
+final TextStyle monospaceStyle = TextStyle(
+  color: Colors.black,
+  fontSize: 14,
+  fontWeight: FontWeight.bold,
+  fontFamily: 'monospace',
+);