...

src/cmd/test/main.go

@@ -39,7 +39,7 @@ func NewPlayer() *Player {
 
 func (p *Player) Start(e *gx.Engine) {
 	c := e.Camera()
-	c.Object.T.RA = gx.V(360, -120)
+	c.Object.T.RA = gx.V(360, -240)
 }
 
 func (p *Player) Update(e *gx.Engine) error {

src/gx/camera.go

@@ -24,11 +24,13 @@ func (c *Camera)RealMatrix(
 ) Matrix {
 	g := &Matrix{}
 
-	// For rotating around.
-	g.Translate(
-		-c.Object.T.RA.X,
-		c.Object.T.RA.Y,
-	)
+
+	if scale {
+		g.Scale(
+			c.Object.T.S.X,
+			c.Object.T.S.Y,
+		)
+	}
 
 	g.Translate(
 		-c.Object.T.P.X,
@@ -41,13 +43,6 @@ func (c *Camera)RealMatrix(
 		-c.Object.T.RA.Y,
 	)
 
-	if scale {
-		g.Scale(
-			c.Object.T.S.X,
-			c.Object.T.S.Y,
-		)
-	}
-
 	return *g
 }
 

src/gx/main.go

@@ -137,6 +137,7 @@ func (e *Engine) DT() Float {
 func (e *Engine) Run() error {
 	ebiten.SetWindowTitle(e.wcfg.Title)
 	ebiten.SetWindowSize(e.wcfg.Width, e.wcfg.Height)
+	ebiten.SetWindowSizeLimits(1, 1, e.wcfg.Width, e.wcfg.Height)
 
 	e.lastTime = time.Now()
 

src/gx/sprite.go

@@ -15,8 +15,9 @@ func (s *Sprite) Draw(
 	i *Image,
 ) {
 	op := &ebiten.DrawImageOptions{}
-	m := s.Object.T.Matrix(e)
+	m := &Matrix{}
 
+	m.Concat(s.Object.T.Matrix(e))
 	if e.camera != nil {
 		m.Concat(e.camera.RealMatrix(
 			e,
@@ -24,7 +25,7 @@ func (s *Sprite) Draw(
 		))
 	}
 
-	op.GeoM = m
+	op.GeoM = *m
 	i.DrawImage(s.Image, op)
 }
 

src/gx/transform.go

@@ -2,6 +2,7 @@ package gx
 
 import (
 	"github.com/hajimehoshi/ebiten/v2"
+	"math"
 )
 
 type Matrix = ebiten.GeoM
@@ -22,6 +23,25 @@ func V(x, y Float) Vector {
 	return Vector{x, y}
 }
 
+// Returns the vector with the matrix applied
+func (v Vector) Apply(m *Matrix) Vector {
+	x, y := m.Apply(v.X, v.Y)
+	return V(x, y)
+}
+
+// Returns the vector rotated by "a" angle in radians.
+func (v Vector) Rotate(a Float) Vector {
+	m := &Matrix{}
+	m.Rotate(a)
+	return v.Apply(m)
+}
+
+// Returns the normalized vector.
+func (v Vector) Norm() Vector {
+	l := math.Sqrt(v.X*v.X + v.Y*v.Y)
+	return V(v.X / l, v.Y / l)
+}
+
 func T() Transform {
 	ret := Transform{}
 	return ret