diff --git a/src/cmd/math/main.go b/src/cmd/math/main.go
index 8891271..b029f3a 100644
--- a/src/cmd/math/main.go
+++ b/src/cmd/math/main.go
@@ -22,6 +22,17 @@ func main() {
 	}
 	
 	for _, l := range lines { fmt.Println(l) }
+	
+	l1 := gx.LineSegment{
+		gx.Point{0, 0},
+		gx.Point{1, 1},
+	}.Line()
+	
+	l2 := gx.LineSegment{
+		gx.Point{0, 1},
+		gx.Point{1, 2},
+	}.Line()
+	fmt.Println(l1.Parallel(l2))
 	/*t := gx.Triangle{
 		gx.Point{0, 0},
 		gx.Point{0, 100},
diff --git a/src/gx/line.go b/src/gx/line.go
index 2dfe1e8..3e65f39 100644
--- a/src/gx/line.go
+++ b/src/gx/line.go
@@ -9,9 +9,24 @@ type Line struct {
 	K, C Float
 }
 
+type Liner interface {
+	Line() Line
+}
+
 // The type represents a line segment.
 type LineSegment [2]Point
 
+// Check whether the liner is parallel to the line.
+func (l Line) Parallel(liner Liner) bool {
+	buf := liner.Line()
+	
+	if buf.K == l.K {
+		return true
+	}
+	
+	return false
+}
+
 // Get square of length of line segment.
 func (ls LineSegment) LenSqr() Float {
 	return Sqr(ls[0].X - ls[1].X) +
@@ -23,6 +38,10 @@ func (ls LineSegment) Len() Float {
 	return math.Sqrt(ls.LenSqr())
 }
 
+func (l Line) Line() Line {
+	return l
+}
+
 // Returns corresponding to the segment line line.
 func (l LineSegment) Line() Line {
 	p0 := l[0]
@@ -34,3 +53,25 @@ func (l LineSegment) Line() Line {
 	return Line{k, c}
 }
 
+
+func (l LineSegment) Crosses(with any) (bool, Point) {
+	switch with.(type) {
+	case Line :
+		return l.crossesLine(with.(Line))
+	case LineSegment :
+		return l.crossesLineSegment(with.(LineSegment))
+	default:
+		panic("The type that is not defined to be crossed")
+	}
+	
+	
+}
+
+func (l LineSegment) crossesLineSegment(with LineSegment) (bool, Point) {
+	return false, Point{}
+}
+
+func (l LineSegment) crossesLine(with Line) (bool, Point) {
+	return false, Point{}
+}
+
diff --git a/src/gx/main.go b/src/gx/main.go
index 2ec580d..70bc9d6 100644
--- a/src/gx/main.go
+++ b/src/gx/main.go
@@ -38,10 +38,6 @@ type Engine struct {
 
 type engine Engine
 
-var (
-	Infinity = math.MaxFloat64
-)
-
 // Return current camera.
 func (e *Engine) Camera() *Camera {
 	return e.camera