diff --git a/Turtle.playground/Sources/What a Turtle Understands/TurtleHeading.swift b/Turtle.playground/Sources/What a Turtle Understands/TurtleHeading.swift
index 4bbecd4..d3bc247 100644
--- a/Turtle.playground/Sources/What a Turtle Understands/TurtleHeading.swift	
+++ b/Turtle.playground/Sources/What a Turtle Understands/TurtleHeading.swift	
@@ -15,7 +15,7 @@ public func right() {
 
 // MARK: - left -
 
-public func left(degrees: Double = 90) {
+public func left(degrees: Double) {
     turtle.increaseHeadingBy(-degrees)
 }