diff --git a/artworld/drawable.js b/artworld/drawable.js
index 0eb0855..9e04729 100644
--- a/artworld/drawable.js
+++ b/artworld/drawable.js
@@ -15,7 +15,7 @@ export class Drawable {
 
   _register() {
     if (this._parent) {
-      this._parent.push(this);
+      this._parent._register(this);
     }
     artworld.register(this);
   }
@@ -26,6 +26,12 @@ export class Drawable {
     return obj;
   }
 
+  draw() {
+    // TODO: log/raise?
+  }
+
+  // setters
+
   fill(color) {
     this._fill = color;
     return this;
@@ -73,7 +79,10 @@ export class Drawable {
   // getters /////////////////////////////
 
   get worldPos() {
-    return this._parent ? this._parent.worldPos.add(this._pos) : this._pos;
+    // offset from parent if needed
+    return this._parent
+      ? this._parent.worldPos.add(this._posVec)
+      : this._posVec;
   }
 }
 
diff --git a/artworld/index.js b/artworld/index.js
index f570896..31f3677 100644
--- a/artworld/index.js
+++ b/artworld/index.js
@@ -1,4 +1,7 @@
 export { artworld } from "./world.js";
 export { Color } from "./color.js";
-export { Vector2 } from "./math.js";
+export { Vector2, degToRad, radToDeg } from "./math.js";
 export { Line } from "./shapes.js";
+export { Group } from "./drawable.js";
+export { Random } from "./random.js";
+console.log("here");
diff --git a/artworld/math.js b/artworld/math.js
index b9ccc21..c4e9c2c 100644
--- a/artworld/math.js
+++ b/artworld/math.js
@@ -1,4 +1,12 @@
-export const TO_RADIANS = 180 / Math.PI;
+const PI_180 = Math.PI / 180;
+
+export function degToRad(degrees) {
+  return degrees * PI_180;
+}
+
+export function radToDeg(rad) {
+  return rad / PI_1i0;
+}
 
 export class Vector2 {
   constructor(x, y) {
@@ -7,15 +15,15 @@ export class Vector2 {
   }
 
   add(other) {
-    return Vector2(this.x + other.x, this.y + other.y);
+    return new Vector2(this.x + other.x, this.y + other.y);
   }
 
   sub(other) {
-    return Vector2(this.x - other.x, this.y - other.y);
+    return new Vector2(this.x - other.x, this.y - other.y);
   }
 
   scale(s) {
-    return Vector2(s * this.x, s * this.y);
+    return new Vector2(s * this.x, s * this.y);
   }
 
   static random(x, y) {
@@ -28,10 +36,10 @@ export class Vector2 {
     if (y === undefined) {
       y = x;
     }
-    return Vector2(x * cos(theta), y * sin(theta));
+    return new Vector2(x * cos(theta), y * sin(theta));
   }
 
   static polar(mag, angle) {
-    return Vector2(mag * Math.cos(angle), mag * Math.sin(angle));
+    return new Vector2(mag * Math.cos(angle), mag * Math.sin(angle));
   }
 }
diff --git a/artworld/random.js b/artworld/random.js
new file mode 100644
index 0000000..1dcd910
--- /dev/null
+++ b/artworld/random.js
@@ -0,0 +1,5 @@
+export class Random {
+  static chance(odds) {
+    return Math.random() < odds;
+  }
+}
diff --git a/artworld/shapes.js b/artworld/shapes.js
index aa58bf9..eaccebf 100644
--- a/artworld/shapes.js
+++ b/artworld/shapes.js
@@ -10,7 +10,7 @@ export class Line extends Drawable {
   draw() {
     artworld.setStrokeColor(this._stroke);
     artworld.setStrokeWeight(this._strokeWeight);
-    artworld.drawLine(this._posVec, this._offsetVec);
+    artworld.drawLine(this.worldPos, this.worldPos.add(this._offsetVec));
   }
 
   to(vec) {
@@ -18,10 +18,6 @@ export class Line extends Drawable {
     return this;
   }
 
-  polar(mag, angle) {
-    return this.to(Vector2.polar(mag, angle));
-  }
-
   angle(angle) {
     let mag = this._offsetVec.magnitude;
     return this.to(Vector2.polar(mag, angle));
diff --git a/artworld/world.js b/artworld/world.js
index 42d2e66..b98507f 100644
--- a/artworld/world.js
+++ b/artworld/world.js
@@ -25,11 +25,13 @@ export class World {
   }
 
   setStrokeColor(color) {
-    this.ctx.strokeStyle = color.toStr();
+    if (color && color.toStr) this.ctx.strokeStyle = color.toStr();
+    else this.ctx.strokeStyle = color;
   }
 
   setFillColor(color) {
-    this.ctx.fillStyle = color.toStr();
+    if (color && color.toStr) this.ctx.fillStyle = color.toStr();
+    else this.ctx.fillStyle = color;
   }
 
   fillRect(rect) {
diff --git a/examples/spiral.html b/examples/spiral.html
new file mode 100644
index 0000000..807d985
--- /dev/null
+++ b/examples/spiral.html
@@ -0,0 +1,58 @@
+<html>
+  <head> </head>
+  <body>
+    <canvas id="mainCanvas" width="800" height="800"></canvas>
+    <script type="module">
+      import {
+        artworld,
+        Color,
+        Group,
+        Line,
+        Random,
+        Vector2,
+        degToRad,
+      } from "../artworld/index.js";
+      artworld.bindCanvas("mainCanvas");
+      window.artworld = artworld;
+
+      function* spirals() {
+        while (true) {
+          let g = new Group();
+          for (let d = 0; d < 180; d += 10) {
+            if (Random.chance(0.9)) {
+              new Line(g).to(Vector2.polar(190 - d, degToRad(d)));
+            }
+          }
+          yield g;
+        }
+      }
+
+      function makeGrid(iterable, rows, cols, opts) {
+        opts = opts || {};
+        let width = opts.width || 50;
+        let height = opts.height || 50;
+        let xOff = opts.xOff || 0;
+        let yOff = opts.yOff || 0;
+        for (let c = 0; c < cols; c++) {
+          for (let r = 0; r < rows; r++) {
+            let result = iterable.next().value;
+            if (result === undefined) {
+              return;
+            } else {
+              result.pos(new Vector2(width * c + xOff, height * r + yOff));
+            }
+          }
+        }
+      }
+
+      makeGrid(spirals(), 4, 3, {
+        width: 220,
+        height: 120,
+        xOff: 80,
+        yOff: 10,
+      });
+
+      artworld.draw();
+    </script>
+  </body>
+</html>