diff --git a/src/main/java/pythagoras/f/AbstractCubicCurve.java b/src/main/java/pythagoras/f/AbstractCubicCurve.java
index 3b78d1c..a0b3526 100644
--- a/src/main/java/pythagoras/f/AbstractCubicCurve.java
+++ b/src/main/java/pythagoras/f/AbstractCubicCurve.java
@@ -33,13 +33,13 @@ public abstract class AbstractCubicCurve implements ICubicCurve
     }
 
     @Override // from interface ICubicCurve
-    public double getFlatnessSq () {
+    public float getFlatnessSq () {
         return CubicCurves.getFlatnessSq(getX1(), getY1(), getCtrlX1(), getCtrlY1(),
                                          getCtrlX2(), getCtrlY2(), getX2(), getY2());
     }
 
     @Override // from interface ICubicCurve
-    public double getFlatness () {
+    public float getFlatness () {
         return CubicCurves.getFlatness(getX1(), getY1(), getCtrlX1(), getCtrlY1(),
                                        getCtrlX2(), getCtrlY2(), getX2(), getY2());
     }
diff --git a/src/main/java/pythagoras/f/AbstractRectangle.java b/src/main/java/pythagoras/f/AbstractRectangle.java
index b70231b..0f0bcbc 100644
--- a/src/main/java/pythagoras/f/AbstractRectangle.java
+++ b/src/main/java/pythagoras/f/AbstractRectangle.java
@@ -114,7 +114,7 @@ public abstract class AbstractRectangle extends RectangularShape implements IRec
     public boolean contains (float rx, float ry, float rw, float rh) {
         if (isEmpty()) return false;
 
-        double x1 = getX(), y1 = getY(), x2 = x1 + getWidth(), y2 = y1 + getHeight();
+        float x1 = getX(), y1 = getY(), x2 = x1 + getWidth(), y2 = y1 + getHeight();
         return (x1 <= rx) && (rx + rw <= x2) && (y1 <= ry) && (ry + rh <= y2);
     }
 
@@ -122,7 +122,7 @@ public abstract class AbstractRectangle extends RectangularShape implements IRec
     public boolean intersects (float rx, float ry, float rw, float rh) {
         if (isEmpty()) return false;
 
-        double x1 = getX(), y1 = getY(), x2 = x1 + getWidth(), y2 = y1 + getHeight();
+        float x1 = getX(), y1 = getY(), x2 = x1 + getWidth(), y2 = y1 + getHeight();
         return (rx + rw > x1) && (rx < x2) && (ry + rh > y1) && (ry < y2);
     }
 
diff --git a/src/main/java/pythagoras/f/ICubicCurve.java b/src/main/java/pythagoras/f/ICubicCurve.java
index edfd83b..84e5a6a 100644
--- a/src/main/java/pythagoras/f/ICubicCurve.java
+++ b/src/main/java/pythagoras/f/ICubicCurve.java
@@ -47,11 +47,11 @@ public interface ICubicCurve extends IShape, Cloneable
 
     /** Returns the square of the flatness (maximum distance of a control point from the line
      * connecting the end points) of this curve. */
-    double getFlatnessSq ();
+    float getFlatnessSq ();
 
     /** Returns the flatness (maximum distance of a control point from the line connecting the end
      * points) of this curve. */
-    double getFlatness ();
+    float getFlatness ();
 
     /** Subdivides this curve and stores the results into {@code left} and {@code right}. */
     void subdivide (CubicCurve left, CubicCurve right);