diff --git a/sketch.js b/sketch.js
index cf036fc..65842a6 100644
--- a/sketch.js
+++ b/sketch.js
@@ -1,12 +1,13 @@
 let charges = [];
 
-let sphere_mode = 'circles';
 let sphere_radius = 200;
 
 let physics = false;
+let earth = false;
+let skeleton = false;
 
 function preload() {
-  earth = loadImage("atlas1.jpg");
+  earth_image = loadImage("atlas1.jpg");
 }
 
 function setup() {
@@ -21,10 +22,32 @@ function draw() {
   if (physics) {
     move_charges(charges);
   }
+  if (skeleton) {
+    draw_skeleton(sphere_radius);
+  }
   draw_charges(sphere_radius);
   draw_sphere(sphere_radius, 25);
 }
 
+function draw_skeleton(radius) {
+  push();
+  noStroke();
+  fill(0xff);
+  sphere(4);
+  stroke(0xbf);
+  for (let charge of charges) {
+    line(
+      0,
+      0,
+      0,
+      charge.position.x * radius,
+      charge.position.y * radius,
+      charge.position.z * radius,
+    );
+  }
+  pop();
+}
+
 function make_charges(n) {
   charges = [];
   for (let i = 0; i < n; i += 1) {
@@ -71,7 +94,7 @@ function draw_sphere(radius, n_axis_circles) {
   rotateX(TAU / 4);
   draw_circles(
     radius,
-    sphere_mode === 'earth' ? 2 : n_axis_circles,
+    earth ? 2 : n_axis_circles,
     color(0x00, 0x9f, 0xff),
     color(0xff, 0x9f, 0x00),
   );
@@ -80,17 +103,17 @@ function draw_sphere(radius, n_axis_circles) {
   rotateY(TAU / 4);
   draw_circles(
     radius,
-    sphere_mode === 'earth' ? 2 : n_axis_circles,
+    earth ? 2 : n_axis_circles,
     color(0xff, 0x00, 0xff),
     color(0x00, 0xff, 0x00),
   );
   pop();
 
-  if (sphere_mode === 'earth') {
+  if (earth) {
     noStroke();
     noFill();
     tint(0xff, 0x9f);
-    texture(earth);
+    texture(earth_image);
     push();
     rotateY(TAU / 4);
     sphere(radius);
@@ -127,10 +150,12 @@ function make_lights() {
 }
 
 function keyPressed() {
-  if (key == 'd') {
-    sphere_mode = sphere_mode === 'earth' ? 'circles' : 'earth';
-  } else if (key == ' ') {
+  if (key == ' ') {
     physics = !physics;
+  } else if (key == 'd') {
+    earth = !earth;
+  } else if (key == 'f') {
+    skeleton = !skeleton;
   } else if (key >= '0' && key <= '9') {
     make_charges(int(key));
   }