diff --git a/.idea/codeStyles/Project.xml b/.idea/codeStyles/Project.xml
index 902b0e4..517ab1f 100644
--- a/.idea/codeStyles/Project.xml
+++ b/.idea/codeStyles/Project.xml
@@ -26,6 +26,7 @@
       <option name="PARENTHESES_EXPRESSION_LPAREN_WRAP" value="true" />
       <option name="PARENTHESES_EXPRESSION_RPAREN_WRAP" value="true" />
       <option name="BINARY_OPERATION_WRAP" value="5" />
+      <option name="WHILE_BRACE_FORCE" value="3" />
       <option name="WRAP_LONG_LINES" value="true" />
       <indentOptions>
         <option name="CONTINUATION_INDENT_SIZE" value="4" />
diff --git a/com/danitheskunk/skunkworks/BaseGame.java b/com/danitheskunk/skunkworks/BaseGame.java
index 3bc2a5f..8f053c0 100644
--- a/com/danitheskunk/skunkworks/BaseGame.java
+++ b/com/danitheskunk/skunkworks/BaseGame.java
@@ -3,24 +3,32 @@ package com.danitheskunk.skunkworks;
 import com.danitheskunk.skunkworks.gfx.IRenderContext;
 import com.danitheskunk.skunkworks.gfx.font.IFont;
 import com.danitheskunk.skunkworks.nodes.Node;
+import com.danitheskunk.skunkworks.nodes.NodeRoot;
+import org.lwjgl.glfw.GLFW;
 
 public abstract class BaseGame {
 	protected Engine engine;
 	protected IWindow window;
 	protected IFont debugFont;
-	protected Node rootNode;
+	protected NodeRoot rootNode;
 
 	public BaseGame(Vec2i windowSize, String windowTitle) {
 		this.engine = new Engine();
 		this.window = engine.openWindow(windowSize, windowTitle);
 		//todo: load from .jar
 		this.debugFont = window.loadFontTileset("fonts/ega-8x14.png");
-		this.rootNode = new Node();
+		this.rootNode = new NodeRoot();
 		init();
 	}
 
 	public void run() {
+		double lastTime, currentTime, delta;
+
+		lastTime = GLFW.glfwGetTime();
 		while(!window.shouldClose()) {
+			currentTime = GLFW.glfwGetTime();
+			delta = currentTime - lastTime;
+			lastTime = currentTime;
 			window.tick();
 			//todo: frame rate control
 			update(1000.0 / 60.0);
diff --git a/com/danitheskunk/skunkworks/Timestep.java b/com/danitheskunk/skunkworks/Timestep.java
new file mode 100644
index 0000000..05ec5e3
--- /dev/null
+++ b/com/danitheskunk/skunkworks/Timestep.java
@@ -0,0 +1,5 @@
+package com.danitheskunk.skunkworks;
+
+public enum Timestep {
+	FIXED, VARIABLE
+}
diff --git a/com/danitheskunk/skunkworks/nodes/BaseTween.java b/com/danitheskunk/skunkworks/nodes/BaseTween.java
new file mode 100644
index 0000000..441c9ee
--- /dev/null
+++ b/com/danitheskunk/skunkworks/nodes/BaseTween.java
@@ -0,0 +1,15 @@
+package com.danitheskunk.skunkworks.nodes;
+
+public abstract class BaseTween {
+	protected double progress;
+
+	public BaseTween() {
+		progress = 0;
+	}
+
+	public void setProgress(double progress) {
+		this.progress = progress;
+	}
+
+	protected abstract void apply();
+}
diff --git a/com/danitheskunk/skunkworks/nodes/Node.java b/com/danitheskunk/skunkworks/nodes/Node.java
index f12b6d3..3688981 100644
--- a/com/danitheskunk/skunkworks/nodes/Node.java
+++ b/com/danitheskunk/skunkworks/nodes/Node.java
@@ -20,6 +20,10 @@ public class Node implements Iterable<Node> {
 		pos = Vec2f.ZERO;
 	}
 
+	public Node getParent() {
+		return parent;
+	}
+
 	public Vec2f getPos() {
 		return pos;
 	}
@@ -52,8 +56,31 @@ public class Node implements Iterable<Node> {
 		return Vec2f.add(parent.getAbsolutePos(), pos);
 	}
 
+	public Node getRoot() {
+		var node = this;
+		while(node.parent != null) {
+			node = node.parent;
+		}
+		return node;
+	}
+
 	@Override
 	public Iterator<Node> iterator() {
 		return children.iterator();
 	}
+
+	public class TweenPos extends BaseTween {
+		private final Vec2f start;
+		private final Vec2f end;
+
+		public TweenPos(Vec2f start, Vec2f end) {
+			this.start = start;
+			this.end = end;
+		}
+
+		@Override
+		protected void apply() {
+			pos = Vec2f.tween(start, end, progress);
+		}
+	}
 }
diff --git a/com/danitheskunk/skunkworks/nodes/NodeRoot.java b/com/danitheskunk/skunkworks/nodes/NodeRoot.java
new file mode 100644
index 0000000..6a331e4
--- /dev/null
+++ b/com/danitheskunk/skunkworks/nodes/NodeRoot.java
@@ -0,0 +1,5 @@
+package com.danitheskunk.skunkworks.nodes;
+
+public class NodeRoot extends Node {
+
+}
diff --git a/com/danitheskunk/skunkworks/nodes/Tweener.java b/com/danitheskunk/skunkworks/nodes/Tweener.java
new file mode 100644
index 0000000..de8dbff
--- /dev/null
+++ b/com/danitheskunk/skunkworks/nodes/Tweener.java
@@ -0,0 +1,11 @@
+package com.danitheskunk.skunkworks.nodes;
+
+import com.danitheskunk.skunkworks.Timestep;
+
+public class Tweener {
+	private Timestep timestepMode;
+
+	public Tweener(Timestep timestepMode) {
+		this.timestepMode = timestepMode;
+	}
+}