added falling sand - dirt actually

Scripts/Elements/Dirt.cs

@@ -3,7 +3,18 @@
 namespace FOU.Scripts.Elements;
 
 public class Dirt : Solid {
-    public Dirt() {
+
+    public Dirt(int x, int y, ref Level level) : base(x, y, ref level) {
         Color = Colors.Brown;
     }
+
+    public override bool Update(int currentFrame) {
+        if (!base.Update(currentFrame)) return false;
+
+        if (CheckBelow(X, Y)) {
+            _level.Swap(this, X, Y+1);
+        }
+        return true;
+    }
+
 }

Scripts/Elements/Element.cs

@@ -2,6 +2,44 @@
 
 namespace FOU.Scripts.Elements;
 
-public abstract class Element {
+public class Element {
     public Color Color = Colors.Black;
+
+    public int X;
+    public int Y;
+
+    protected Level _level;
+
+    private int _lastUpdate = -1;
+
+    public Element(int x, int y, ref Level level) {
+        X = x;
+        Y = y;
+        _level = level;
+    }
+
+    /// <summary>
+    /// base update method, checks if anything is to do at all
+    /// </summary>
+    /// <param name="currentFrame"></param>
+    /// <returns>false if there is nothing to do</returns>
+    public virtual bool Update(int currentFrame) {
+        if (_lastUpdate == currentFrame) return false; // already updated this frame
+        _lastUpdate = currentFrame;
+
+        return true;
+    }
+
+    public override string ToString() {
+        return $"{X}:{Y}";
+    }
+
+    protected bool CheckBelow(int x, int y) {
+        if (y+1 >= _level.SizeY) return false;
+
+        if (_level.Get(x, y+1).GetType() == GetType())
+            return false;
+
+        return true;
+    }
 }

Scripts/Elements/Solid.cs

@@ -1,5 +1,5 @@
 namespace FOU.Scripts.Elements;
 
 public abstract class Solid : Element {
-
+    protected Solid(int x, int y, ref Level level) : base(x, y, ref level) { }
 }