diff --git a/src/geom.rs b/src/geom.rs
index 3df765c..d343683 100644
--- a/src/geom.rs
+++ b/src/geom.rs
@@ -124,7 +124,7 @@ impl Line {
         if self.is_ascending_x() {
             x >= self.from.x && x < self.to.x
         } else {
-            x >= self.to.x && x < self.from.x
+            x <= self.from.x && x > self.to.x
         }
     }
 
@@ -133,17 +133,24 @@ impl Line {
         if self.is_ascending_x() {
             y >= self.from.y && y < self.to.y
         } else {
-            y >= self.to.y && y < self.from.y
+            y <= self.from.y && y > self.to.y
         }
     }
 
+    pub fn min_x(&self) -> f64 {
+        self.from.x.min(self.to.x).into()
+    }
+
+    pub fn max_x(&self) -> f64 {
+        self.from.x.max(self.to.x).into()
+    }
+
     pub fn clamp_x(&self, x: f64) -> f64 {
-        let x = real(x);
         match x {
-            v if v < self.from.x => self.from.x,
-            v if v > self.to.x => self.to.x,
+            v if v < self.min_x() => self.min_x(),
+            v if v > self.max_x() => self.max_x(),
             v => v,
-        }.into()
+        }
     }
 
     pub fn clamp_by_x(&self, x: f64) -> Point {
diff --git a/src/mat.rs b/src/mat.rs
index 26deee6..5f2949c 100644
--- a/src/mat.rs
+++ b/src/mat.rs
@@ -228,14 +228,14 @@ mod test {
     #[test]
     fn mh_curve_move_from_inner_to_inner() {
         let curve = mh_curve_for_test();
-        assert_eq!(curve.move_to(0.0, 0.0, 5.0), (5.0, 0.0));
-        assert_eq!(curve.move_to(0.0, 5.0, 10.0), (5.0, 5.0));
+        assert_eq!(curve.step_toward(0.0, 0.0, 5.0), Ok((5.0, 0.0)));
+        assert_eq!(curve.step_toward(0.0, 5.0, 10.0), Ok((5.0, 5.0)));
 
-        assert_eq!(curve.move_to(-5.0, 5.0, -3.0), (-8.0, 5.0));
-        assert_eq!(curve.move_to(-5.0, 5.0, 7.0), (2.0, 5.0));
+        assert_eq!(curve.step_toward(-5.0, 5.0, -3.0), Ok((-8.0, 5.0)));
+        assert_eq!(curve.step_toward(-5.0, 5.0, 7.0), Ok((2.0, 5.0)));
 
-        assert_eq!(curve.move_to(5.0, -5.0, -3.0), (2.0, -5.0));
-        assert_eq!(curve.move_to(5.0, -5.0, 3.0), (8.0, -5.0));
+        assert_eq!(curve.step_toward(5.0, -5.0, -3.0), Ok((2.0, -5.0)));
+        assert_eq!(curve.step_toward(5.0, -5.0, 3.0), Ok((8.0, -5.0)));
     }
 
     #[test]
@@ -252,4 +252,19 @@ mod test {
         // middle of segment to end of segment
         assert_eq!(curve.step_toward(12.0, 20.0, 120.0), Err((20.0, 100.0)));
     }
+
+    #[test]
+    fn mh_curve_ascend_along_negative_edge() {
+        let curve = mh_curve_for_test();
+        // start of segment to middle of segment
+        assert_eq!(curve.step_toward(-10.0, 0.0, -32.0), Ok((-12.0, -20.0)));
+        // start of segment NOOP
+        assert_eq!(curve.step_toward(-10.0, 0.0, -10.0), Ok((-10.0, 0.0)));
+        // middle of segment NOOP
+        assert_eq!(curve.step_toward(-12.0, -20.0, -32.0), Ok((-12.0, -20.0)));
+        // middle of segment to middle of segment
+        assert_eq!(curve.step_toward(-12.0, -20.0, -54.0), Ok((-14.0, -40.0)));
+        // middle of segment to end of segment
+        assert_eq!(curve.step_toward(-12.0, -20.0, -120.0), Err((-20.0, -100.0)));
+    }
 }