diff --git a/src/graphics.ts b/src/graphics.ts
index 521357e5..2f3ace59 100644
--- a/src/graphics.ts
+++ b/src/graphics.ts
@@ -1,17 +1,42 @@
 import * as core from "graphics-core";
 
-// Clear the screen to the specified color. r, g, and b should vary from 0 to
-// 1.
+/**
+ * Clear the screen.
+ *
+ * @param r - The red component of the color to clear to, from 0 to 1.
+ * @param g - The green component of the color to clear to, from 0 to 1.
+ * @param b - The blue component of the color to clear to, from 0 to 1.
+ */
 export function cls(r: number, g: number, b: number) {
   core.cls(r, g, b);
 }
 
-// Print a message to the console.
+/**
+ * Print a message to the console.
+ *
+ * @remarks
+ * The specified arguments will be printed to the console, one at a time,
+ * separated by spaces. If you want them separated by something else,
+ * format the string yourself.
+ *
+ * @param args - Arguments to print to the console.
+ */
 export function print(...args: unknown[]) {
   core.print(args.join(" "));
 }
 
-// Draw a sprite in the rectangle from x,y to
+/**
+ * Draw a sprite.
+ *
+ * @param x - The x coordinate of the upper-left pixel of the sprite.
+ * @param y - The y coordinate of the upper-left pixel of the sprite.
+ * @param w - The width of the target rectangle, in pixels.
+ * @param h - The height of the target rectangle, in pixels.
+ * @param sx - The x offset of the upper-left pixel of the sprite in the current sheet, in pixels.
+ * @param sy - The y offset of the upper-left pixel of the sprite in the current sheet, in pixels.
+ * @param sw - The width of the sprite, in pixels. If null or not specified, defaults to the width of the target rectangle.
+ * @param sh - The height of the sprite, in pixels. If null or not specified, defaults to the height of the target rectangle.
+ */
 export function spr(
   x: number,
   y: number,
@@ -19,8 +44,10 @@ export function spr(
   h: number,
   sx: number,
   sy: number,
-  sw: number,
-  sh: number
+  sw: number | null = null,
+  sh: number | null = null
 ) {
+  sw = sw || w;
+  sh = sh || h;
   core.spr(x, y, w, h, sx, sy, sw, sh);
 }
diff --git a/src/main.ts b/src/main.ts
index 22331375..4306f38d 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -8,5 +8,5 @@ export function update() {}
 
 export function draw() {
   cls(0.1, 0.2, 0.3);
-  spr(0, 0, 320, 240, 0, 0, 256, 256);
+  spr((320 - 256) / 2, 0, 256, 240, 0, 0);
 }