refact

lib/rabbit.go

@@ -0,0 +1,40 @@
+package lib
+
+import (
+	"math"
+	"math/rand"
+
+	"github.com/hajimehoshi/ebiten/v2"
+)
+
+type Rabbit struct {
+	Lane  int
+	T     float64
+	Speed float64
+}
+
+// newRabbit spawns a rabbit at the horizon with a speed that ramps up with score.
+func newRabbit(score int) *Rabbit {
+	return &Rabbit{
+		Lane:  rand.Intn(LaneCount),
+		Speed: 0.010 + rand.Float64()*0.006 + math.Min(float64(score), 60)*0.0002,
+	}
+}
+
+// Position returns the on-screen pixel position along the perspective curve.
+func (r *Rabbit) Position() (float32, float32) {
+	endX := float64(LaneX[r.Lane])
+	endY := PlayerY - 6.0
+	x := HorizonX + (endX-HorizonX)*(r.T*r.T)
+	y := HorizonY + (endY-HorizonY)*r.T
+	hop := math.Abs(math.Sin(r.T*14)) * (2 + r.T*4)
+	return float32(x), float32(y - hop)
+}
+
+// Draw renders the rabbit, growing from the horizon and cycling hop frames.
+func (r *Rabbit) Draw(dst *ebiten.Image, frames [4]*ebiten.Image) {
+	x, y := r.Position()
+	h := float32(6 + r.T*22)
+	frame := frames[int(r.T*16)%len(frames)]
+	blitH(dst, frame, x, y+h/2, h)
+}