diff --git a/src/main/java/puzzle/SwedishGenerator.java b/src/main/java/puzzle/SwedishGenerator.java
index 73321af..734d0f1 100644
--- a/src/main/java/puzzle/SwedishGenerator.java
+++ b/src/main/java/puzzle/SwedishGenerator.java
@@ -17,6 +17,14 @@ import java.util.function.Predicate;
 @SuppressWarnings("ALL")
 public record SwedishGenerator(int W, int H, int SIZE, int MAX_LEN) {
    
+   class Data {
+      
+      static byte[] EXAMPLE = new byte[0];
+   }
+   public SwedishGenerator {
+      Data.EXAMPLE = new byte[SIZE];
+      Arrays.fill(Data.EXAMPLE, (byte) '#');
+   }
    public SwedishGenerator(int W, int H) { this(W, H, W * H, Math.min(W, H)); }
    public SwedishGenerator()             { this(9, 8); }
    
@@ -91,7 +99,7 @@ public record SwedishGenerator(int W, int H, int SIZE, int MAX_LEN) {
       int getOffset(int r, int c) { return r * W + c; }
       
       boolean isLettercell(int r, int c) {
-         return isLetterCell(getCharAt(r,c));
+         return isLetterCell(getCharAt(r, c));
       }
       char getCharAt(int r, int c) {
          return (char) (g[getOffset(r, c)] & 0xFF);
@@ -113,9 +121,7 @@ public record SwedishGenerator(int W, int H, int SIZE, int MAX_LEN) {
    }
    // ---------------- Grid helpers ----------------
    Grid makeEmptyGrid() {
-      var g = new byte[H * W];
-      Arrays.fill(g, (byte) '#');
-      return new Grid(g, H, W);
+      return new Grid(Data.EXAMPLE.clone(), H, W);
    }
    
    String gridToString(Grid g) {
@@ -670,9 +676,9 @@ public record SwedishGenerator(int W, int H, int SIZE, int MAX_LEN) {
       var n   = 0;
       
       for (var i = 0; i < s.len; i++) {
-         int r      = s.rs[i], c = s.cs[i];
-         char cur   = grid.getCharAt(r, c);
-         var ch     = w.charAt(i);
+         int  r   = s.rs[i], c = s.cs[i];
+         char cur = grid.getCharAt(r, c);
+         var  ch  = w.charAt(i);
          if (cur == '#') {
             urs[n] = r;
             ucs[n] = c;
diff --git a/src/test/java/puzzle/MainTest.java b/src/test/java/puzzle/MainTest.java
index 6d7a7a8..60ff6ca 100644
--- a/src/test/java/puzzle/MainTest.java
+++ b/src/test/java/puzzle/MainTest.java
@@ -1,6 +1,9 @@
 package puzzle;
 
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
 import puzzle.SwedishGenerator.Dict;
+import puzzle.SwedishGenerator.Grid;
 import puzzle.SwedishGenerator.Lemma;
 import puzzle.SwedishGenerator.PuzzleResult;
 import puzzle.SwedishGenerator.Rng;
@@ -9,7 +12,81 @@ import static puzzle.Main.indentLines;
 public class MainTest {
    
    public static void main(String[] args) {
-      new MainTest().testAttempt();
+      MainTest t = new MainTest();
+      t.testGridBasics();
+      t.testGridDeepCopy();
+      t.testGridOffset();
+      t.testMini();
+      t.testAttempt();
+   }
+   
+   @Test
+   public void testGridBasics() {
+      var grid = new Grid(new byte[3 * 4], 3, 4);
+      // Initialize with #
+      for (int r = 0; r < 3; r++) {
+         for (int c = 0; c < 4; c++) {
+            grid.setCharAt(r, c, '#');
+         }
+      }
+
+      // Test set/get
+      grid.setCharAt(0, 0, 'A');
+      grid.setCharAt(1, 2, '5');
+      grid.setCharAt(2, 3, 'Z');
+
+      Assertions.assertEquals('A', grid.getCharAt(0, 0));
+      Assertions.assertEquals('5', grid.getCharAt(1, 2));
+      Assertions.assertEquals('Z', grid.getCharAt(2, 3));
+      Assertions.assertEquals('#', grid.getCharAt(1, 1));
+
+      // Test isLetterAt
+      Assertions.assertTrue(grid.isLetterAt(0, 0));
+      Assertions.assertFalse(grid.isLetterAt(1, 2));
+      Assertions.assertTrue(grid.isLetterAt(2, 3));
+      Assertions.assertFalse(grid.isLetterAt(1, 1));
+
+      // Test isDigitAt
+      Assertions.assertFalse(grid.isDigitAt(0, 0));
+      Assertions.assertTrue(grid.isDigitAt(1, 2));
+      Assertions.assertFalse(grid.isDigitAt(2, 3));
+      Assertions.assertFalse(grid.isDigitAt(1, 1));
+
+      // Test isLettercell
+      Assertions.assertTrue(grid.isLettercell(0, 0)); // 'A' is letter
+      Assertions.assertFalse(grid.isLettercell(1, 2)); // '5' is digit
+      Assertions.assertTrue(grid.isLettercell(1, 1)); // '#' is lettercell
+   }
+
+   @Test
+   public void testGridDeepCopy() {
+      var grid = new Grid(new byte[2 * 2], 2, 2);
+      grid.setCharAt(0, 0, 'A');
+      grid.setCharAt(0, 1, 'B');
+      grid.setCharAt(1, 0, 'C');
+      grid.setCharAt(1, 1, 'D');
+
+      var copy = grid.deepCopyGrid();
+      Assertions.assertEquals('A', copy.getCharAt(0, 0));
+      
+      copy.setCharAt(0, 0, 'X');
+      Assertions.assertEquals('X', copy.getCharAt(0, 0));
+      Assertions.assertEquals('A', grid.getCharAt(0, 0)); // Original should be unchanged
+   }
+
+   @Test
+   public void testGridOffset() {
+      var grid = new Grid(new byte[10 * 10], 10, 10);
+      Assertions.assertEquals(0, grid.getOffset(0, 0));
+      Assertions.assertEquals(11, grid.getOffset(1, 1));
+      Assertions.assertEquals(99, grid.getOffset(9, 9));
+   }
+
+   @Test
+   public void testMini() {
+      var grid = new Grid(new byte[3 * 3], 3, 3);
+      grid.setCharAt(1, 1, '1');
+      Assertions.assertTrue(grid.isDigitAt(1, 1));
    }
    
    public void testAttempt() {