diff --git a/balance/README.md b/balance/README.md
new file mode 100644
index 0000000..7ece450
--- /dev/null
+++ b/balance/README.md
@@ -0,0 +1,33 @@
+# balance
+
+Constants and settings for the Doodle app.
+
+## Environment Variables
+
+Some runtime settings can be configured in the environment. Here they are
+with their default values.
+
+Most colors work with alpha channels; just provide an 8 hex character code,
+like `#FF00FF99` for 153 ($99) on the alpha channel.
+
+* Application Windw Size (ints):
+  * `DOODLE_W=1024`
+  * `DOODLE_H=768`
+* Shell settings:
+  * `D_SHELL_BG=#001428C8`: shell background color.
+  * `D_SHELL_FG=#0099FF`: shell text color.
+  * `D_SHELL_PC=#FFFFFF`: shell prompt color.
+  * `D_SHELL_LN=8`: shell history line count (how tall the shell is in lines)
+  * `D_SHELL_FS=16`: font size for both the shell and on-screen flashed
+    messages.
+* Debug Colors and Hitboxes (default invisible=off):
+  * `DEBUG_CHUNK_COLOR=#FFFFFF`: background color when caching a
+    chunk to bitmap. Helps visualize where the chunks and caching
+    are happening.
+  * `DEBUG_CANVAS_BORDER`: draw a border color around every uix.Canvas
+    widget. This effectively draws the bounds of every Doodad drawn on top
+    of a level or inside a button and the bounds of the level space itself.
+* Tuning constants (may not be available in production builds):
+  * `D_SCROLL_SPEED=8`: Canvas scroll speed when using the keyboard arrows
+    in the Editor Mode, in pixels per tick.
+  * `D_DOODAD_SIZE=100`: Default size when creating a new Doodad.
diff --git a/balance/debug.go b/balance/debug.go
index 0b8f86e..12548e9 100644
--- a/balance/debug.go
+++ b/balance/debug.go
@@ -1,7 +1,9 @@
 package balance
 
 import (
+	"fmt"
 	"os"
+	"strconv"
 
 	"git.kirsle.net/apps/doodle/render"
 )
@@ -17,10 +19,63 @@ var (
 	// on disk. Default is white. Setting this to translucent yellow is a great
 	// way to visualize the chunks loaded from cache on your screen.
 	DebugChunkBitmapBackground = render.White // XXX: export $DEBUG_CHUNK_COLOR
+
+	// Put a border around all Canvas widgets.
+	DebugCanvasBorder = render.Red
 )
 
 func init() {
-	if color := os.Getenv("DEBUG_CHUNK_COLOR"); color != "" {
-		DebugChunkBitmapBackground = render.MustHexColor(color)
+	// Load values from environment variables.
+	var config = map[string]interface{}{
+		// Window size.
+		"DOODLE_W": &Width,
+		"DOODLE_H": &Height,
+
+		// Tune some parameters. XXX: maybe dangerous at some point.
+		"D_SCROLL_SPEED": &CanvasScrollSpeed,
+		"D_DOODAD_SIZE":  &DoodadSize,
+
+		// Shell settings.
+		"D_SHELL_BG": &ShellBackgroundColor,
+		"D_SHELL_FG": &ShellForegroundColor,
+		"D_SHELL_PC": &ShellPromptColor,
+		"D_SHELL_LN": &ShellHistoryLineCount,
+		"D_SHELL_FS": &ShellFontSize,
+
+		// Visualizers
+		"DEBUG_CHUNK_COLOR":   &DebugChunkBitmapBackground,
+		"DEBUG_CANVAS_BORDER": &DebugCanvasBorder,
+	}
+	for name, value := range config {
+		switch v := value.(type) {
+		case *int:
+			*v = IntEnv(name, *(v))
+		case *int32:
+			*v = int32(IntEnv(name, int(*(v))))
+		case *render.Color:
+			*v = ColorEnv(name, *(v))
+		}
 	}
 }
+
+// ColorEnv gets a color value from environment variable or returns a default.
+// This will panic if the color is not valid, so only do this on startup time.
+func ColorEnv(name string, v render.Color) render.Color {
+	if color := os.Getenv(name); color != "" {
+		fmt.Printf("set %s to %s\n", name, color)
+		return render.MustHexColor(color)
+	}
+	return v
+}
+
+// IntEnv gets an int value from environment variable or returns a default.
+func IntEnv(name string, v int) int {
+	if env := os.Getenv(name); env != "" {
+		a, err := strconv.Atoi(env)
+		if err != nil {
+			panic(err)
+		}
+		return a
+	}
+	return v
+}