feat: scale speed based on level

src/main/java/eu/midnightdust/yaytris/game/Space.java

@@ -13,6 +13,7 @@ public class Space {
     private TetrominoShape nextShape;
     private Tetromino currentTetromino;
     private int score;
+    public int level;
 
     public Space() {
         gameMap = new Color[14][8];
@@ -79,7 +80,7 @@ public class Space {
                 gameMap[line][i] = newBlobs[i];
             }
             if (Arrays.stream(gameMap[line]).noneMatch(Objects::isNull)) { // Line completed
-                combo += 10;
+                combo += 40;
                 completedLines.add(line);
                 combo *= completedLines.size();
             }