Just use pixel/pixelgl directly for the visual example

examples/canvas/main.go

@@ -1,136 +0,0 @@
-package main
-
-import (
-	"time"
-
-	"github.com/charmbracelet/harmonica"
-	"github.com/h8gi/canvas"
-)
-
-const (
-	canvasWidth  = 1024
-	canvasHeight = 768
-	fps          = 60
-	circleRadius = 100
-	bgColor      = "#111111"
-	idleTimeout  = time.Second * 5
-)
-
-type State int
-
-const (
-	unstarted State = iota
-	running
-	timeout
-)
-
-func main() {
-	var (
-		circ      Circle
-		state     State
-		lastClick time.Time
-	)
-
-	c := canvas.NewCanvas(&canvas.CanvasConfig{
-		Width:     canvasWidth,
-		Height:    canvasHeight,
-		FrameRate: fps,
-		Title:     "Harmonica",
-	})
-
-	c.Draw(func(ctx *canvas.Context) {
-		ctx.Clear()
-		ctx.SetHexColor(bgColor)
-
-		switch state {
-		case unstarted:
-			if ctx.IsMouseDragged {
-				const frequency = 0.8
-				const damping = 1.0
-
-				circ = Circle{
-					// Setup a new spring.
-					spring: harmonica.NewSpring(harmonica.FPS(fps), frequency, damping),
-
-					// Set target radius.
-					Radius: circleRadius,
-				}
-
-				// Set starting position.
-				circ.SetPos(ctx.Mouse.X, ctx.Mouse.Y)
-
-				lastClick = time.Now()
-				state = running
-			}
-
-		case running:
-			if ctx.IsMouseDragged {
-				lastClick = time.Now()
-
-				if circ.Hidden {
-					circ.SetPos(ctx.Mouse.X, ctx.Mouse.Y)
-					circ.Hidden = false
-				}
-
-				// Update targets for our spring animation.
-				circ.X = ctx.Mouse.X
-				circ.Y = ctx.Mouse.Y
-				circ.Radius = circleRadius
-			}
-
-			circ.Draw(ctx)
-
-			if time.Now().After(lastClick.Add(idleTimeout)) {
-				state = timeout
-			}
-
-		case timeout:
-			circ.Radius = 0
-			circ.Draw(ctx)
-			if circ.rad == 0 {
-				state = running
-				lastClick = time.Now()
-			}
-		}
-	})
-}
-
-type Circle struct {
-	// Target values. This is what the spring will use as an equilibrium to
-	// animate towards.
-	X, Y, Radius float64
-
-	x, xVel     float64
-	y, yVel     float64
-	rad, radVel float64
-	spring      harmonica.Spring
-
-	Hidden bool
-}
-
-func (c *Circle) SetPos(x, y float64) {
-	c.x = x
-	c.y = y
-	c.Hidden = false
-}
-
-func (c *Circle) Draw(ctx *canvas.Context) {
-	// Update position and radius.
-	c.spring.Update(&c.x, &c.xVel, c.X)
-	c.spring.Update(&c.y, &c.yVel, c.Y)
-	c.spring.Update(&c.rad, &c.radVel, c.Radius)
-
-	if c.rad < 0 {
-		c.rad = 0
-		c.radVel = 0
-		c.Hidden = true
-	}
-
-	const color = "#f1f1f1"
-
-	ctx.Push()
-	ctx.DrawCircle(c.x, c.y, c.rad)
-	ctx.SetHexColor(color)
-	ctx.Fill()
-	ctx.Pop()
-}

examples/go.mod

@@ -5,12 +5,10 @@ go 1.16
 replace github.com/charmbracelet/harmonica => ../
 
 require (
-	github.com/charmbracelet/bubbletea v0.14.1 // indirect
+	github.com/charmbracelet/bubbletea v0.14.1
-	github.com/charmbracelet/harmonica v0.0.0-20210709144143-16876a63b30d // indirect
+	github.com/charmbracelet/harmonica v0.0.0-20210709144143-16876a63b30d
-	github.com/charmbracelet/lipgloss v0.3.0 // indirect
+	github.com/charmbracelet/lipgloss v0.3.0
-	github.com/google/goterm v0.0.0-20190703233501-fc88cf888a3f // indirect
+	github.com/faiface/pixel v0.10.0
-	github.com/h8gi/canvas v0.0.0-20200710004640-a6361a06ab49
+	github.com/fogleman/gg v1.3.0
-	github.com/pkg/term v0.0.0-20200520122047-c3ffed290a03 // indirect
-	golang.org/x/crypto v0.0.0-20201012173705-84dcc777aaee // indirect
 	golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff
 )

examples/go.sum

@@ -4,30 +4,28 @@ github.com/charmbracelet/lipgloss v0.3.0 h1:5MysOD6sHr4RP4jkZNWGVIul5GKoOsP12Ngb
 github.com/charmbracelet/lipgloss v0.3.0/go.mod h1:VkhdBS2eNAmRkTwRKLJCFhCOVkjntMusBDxv7TXahuk=
 github.com/containerd/console v1.0.1 h1:u7SFAJyRqWcG6ogaMAx3KjSTy1e3hT9QxqX7Jco7dRc=
 github.com/containerd/console v1.0.1/go.mod h1:XUsP6YE/mKtz6bxc+I8UiKKTP04qjQL4qcS3XoQ5xkw=
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380 h1:FvZ0mIGh6b3kOITxUnxS3tLZMh7yEoHo75v3/AgUqg0=
 github.com/faiface/glhf v0.0.0-20181018222622-82a6317ac380/go.mod h1:zqnPFFIuYFFxl7uH2gYByJwIVKG7fRqlqQCbzAnHs9g=
 github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3 h1:baVdMKlASEHrj19iqjARrPbaRisD7EuZEVJj6ZMLl1Q=
 github.com/faiface/mainthread v0.0.0-20171120011319-8b78f0a41ae3/go.mod h1:VEPNJUlxl5KdWjDvz6Q1l+rJlxF2i6xqDeGuGAxa87M=
-github.com/faiface/pixel v0.8.0 h1:phOHW6ixfMAKRamjnvhI6FFI2VRyPEq7+LmmkDGXB/4=
+github.com/faiface/pixel v0.10.0 h1:EHm3ZdQw2Ck4y51cZqFfqQpwLqNHOoXwbNEc9Dijql0=
-github.com/faiface/pixel v0.8.0/go.mod h1:CEUU/s9E82Kqp01Boj1O67KnBskqiLghANqvUJGgDAM=
+github.com/faiface/pixel v0.10.0/go.mod h1:lU0YYcW77vL0F1CG8oX51GXurymL45MXd57otHNLK7A=
 github.com/fogleman/gg v1.3.0 h1:/7zJX8F6AaYQc57WQCyN9cAIz+4bCJGO9B+dyW29am8=
 github.com/fogleman/gg v1.3.0/go.mod h1:R/bRT+9gY/C5z7JzPU0zXsXHKM4/ayA+zqcVNZzPa1k=
 github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7 h1:SCYMcCJ89LjRGwEa0tRluNRiMjZHalQZrVrvTbPh+qw=
 github.com/go-gl/gl v0.0.0-20190320180904-bf2b1f2f34d7/go.mod h1:482civXOzJJCPzJ4ZOX/pwvXBWSnzD4OKMdH4ClKGbk=
-github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1 h1:QbL/5oDUmRBzO9/Z7Seo6zf912W/a6Sr4Eu0G/3Jho0=
+github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72 h1:b+9H1GAsx5RsjvDFLoS5zkNBzIQMuVKUYQDmxU3N5XE=
-github.com/go-gl/glfw v0.0.0-20190409004039-e6da0acd62b1/go.mod h1:vR7hzQXu2zJy9AVAgeJqvqgH9Q5CA+iKCZ2gyEVpxRU=
+github.com/go-gl/glfw/v3.3/glfw v0.0.0-20191125211704-12ad95a8df72/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
 github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7 h1:THttjeRn1iiz69E875U6gAik8KTWk/JYAHoSVpUxBBI=
 github.com/go-gl/mathgl v0.0.0-20190416160123-c4601bc793c7/go.mod h1:yhpkQzEiH9yPyxDUGzkmgScbaBVlhC06qodikEM0ZwQ=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
-github.com/google/goterm v0.0.0-20190703233501-fc88cf888a3f/go.mod h1:nOFQdrUlIlx6M6ODdSpBj1NVA+VgLC6kmw60mkw34H4=
-github.com/h8gi/canvas v0.0.0-20200710004640-a6361a06ab49 h1:svddC2dRqy+Y1zGH4+AvvCFZLKuPhAfEvlgYSNP4lcg=
-github.com/h8gi/canvas v0.0.0-20200710004640-a6361a06ab49/go.mod h1:7iSUKfOcA+GiWc+LpxXggMogUFIo8pm1FZcYTUmL3YY=
 github.com/lucasb-eyer/go-colorful v1.2.0 h1:1nnpGOrhyZZuNyfu1QjKiUICQ74+3FNCN69Aj6K7nkY=
 github.com/lucasb-eyer/go-colorful v1.2.0/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/mattn/go-isatty v0.0.12 h1:wuysRhFDzyxgEmMf5xjvJ2M9dZoWAXNNr5LSBS7uHXY=
 github.com/mattn/go-isatty v0.0.12/go.mod h1:cbi8OIDigv2wuxKPP5vlRcQ1OAZbq2CE4Kysco4FUpU=
-github.com/mattn/go-runewidth v0.0.10 h1:CoZ3S2P7pvtP45xOtBw+/mDL2z0RKI576gSkzRRpdGg=
 github.com/mattn/go-runewidth v0.0.10/go.mod h1:RAqKPSqVFrSLVXbA8x7dzmKdmGzieGRCM46jaSJTDAk=
 github.com/mattn/go-runewidth v0.0.13 h1:lTGmDsbAYt5DmK6OnoV7EuIF1wEIFAcxld6ypU4OSgU=
 github.com/mattn/go-runewidth v0.0.13/go.mod h1:Jdepj2loyihRzMpdS35Xk/zdY8IAYHsh153qUoGf23w=
@@ -35,25 +33,22 @@ github.com/muesli/reflow v0.2.1-0.20210115123740-9e1d0d53df68 h1:y1p/ycavWjGT9Fn
 github.com/muesli/reflow v0.2.1-0.20210115123740-9e1d0d53df68/go.mod h1:Xk+z4oIWdQqJzsxyjgl3P22oYZnHdZ8FFTHAQQt5BMQ=
 github.com/muesli/termenv v0.8.1 h1:9q230czSP3DHVpkaPDXGp0TOfAwyjyYwXlUCQxQSaBk=
 github.com/muesli/termenv v0.8.1/go.mod h1:kzt/D/4a88RoheZmwfqorY3A+tnsSMA9HJC/fQSFKo0=
-github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
 github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
 github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
 github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
-github.com/pkg/term v0.0.0-20200520122047-c3ffed290a03/go.mod h1:Z9+Ul5bCbBKnbCvdOWbLqTHhJiYV414CURZJba6L8qA=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/rivo/uniseg v0.1.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
 github.com/rivo/uniseg v0.2.0 h1:S1pD9weZBuJdFmowNwbpi7BJ8TNftyUImj/0WQi72jY=
 github.com/rivo/uniseg v0.2.0/go.mod h1:J6wj4VEh+S6ZtnVlnTBMWIodfgj8LQOQFoIToxlJtxc=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-golang.org/x/crypto v0.0.0-20201012173705-84dcc777aaee/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+github.com/stretchr/testify v1.3.0 h1:TivCn/peBQ7UY8ooIcPgZFpTNSz0Q2U6UrFlUfqbe0Q=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 golang.org/x/image v0.0.0-20190321063152-3fc05d484e9f/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
 golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff h1:+2zgJKVDVAz/BWSsuniCmU1kLCjL88Z8/kv39xCI9NQ=
 golang.org/x/image v0.0.0-20190523035834-f03afa92d3ff/go.mod h1:kZ7UVZpmo3dzQBMxlp+ypCbDeSB+sBbTgSJuh5dn5js=
-golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200916030750-2334cc1a136f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 h1:nxC68pudNYkKU6jWhgrqdreuFiOQWj1Fs7T3VrH4Pjw=
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4 h1:myAQVi0cGEoqQVR5POX+8RR2mrocKqNN1hmeMqhX27k=
 golang.org/x/sys v0.0.0-20210119212857-b64e53b001e4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=

examples/pixel/main.go

@@ -0,0 +1,332 @@
+package main
+
+import (
+	"fmt"
+	"image"
+	"math"
+	"math/rand"
+	"time"
+
+	"github.com/charmbracelet/harmonica"
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/pixelgl"
+	"github.com/fogleman/gg"
+	"golang.org/x/image/font"
+)
+
+const (
+	width       = 1024
+	height      = 768
+	fontFile    = "JetBrainsMono-Regular.ttf"
+	idleTimeout = time.Second * 4
+)
+
+func main() {
+	rand.Seed(time.Now().UnixNano())
+	pixelgl.Run(Game{}.Run)
+}
+
+type Game struct {
+	deltaTime   float64
+	frequency   float64
+	damping     float64
+	win         *pixelgl.Window
+	bgColor     string
+	textColor   string
+	spriteColor string
+	shift       bool
+	font        font.Face
+	sprite      *Sprite
+	lastClick   time.Time
+	dirty       bool
+	showHelp    bool
+}
+
+func (g Game) Size() (width, height float64) {
+	return g.win.Bounds().W(), g.win.Bounds().H()
+}
+
+func (g Game) MousePosition() (x, y float64) {
+	return g.win.MousePosition().X, g.win.MousePosition().Y
+}
+
+func (g Game) Run() {
+	g.frequency = 2.0
+	g.damping = 2.0
+	g.bgColor = "#575BD8"
+	g.textColor = "#827EFF"
+	g.spriteColor = "#FFFDF5"
+	g.showHelp = true
+
+	var err error
+	if g.font, err = gg.LoadFontFace(fontFile, 24); err != nil {
+		panic(err)
+	}
+
+	cfg := pixelgl.WindowConfig{
+		Title:     "Harmonica Example",
+		Bounds:    pixel.R(0, 0, width, height),
+		VSync:     true,
+		Resizable: false,
+	}
+
+	if g.win, err = pixelgl.NewWindow(cfg); err != nil {
+		panic(err)
+	}
+
+	last := time.Now()
+	for !g.win.Closed() {
+		w, h := g.Size()
+
+		// Get delta time
+		g.deltaTime = time.Since(last).Seconds()
+		last = time.Now()
+
+		g.Update()
+
+		// Use fogleman/gg to render everything
+		ctx := gg.NewContext(int(w), int(h))
+		g.Draw(ctx)
+		canvas := g.win.Canvas()
+		canvas.SetPixels(ctx.Image().(*image.RGBA).Pix)
+
+		// Render
+		g.win.Update()
+	}
+}
+
+func (g *Game) Update() {
+	pressed := g.win.JustPressed
+	released := g.win.JustReleased
+
+	// Handle shift key
+	switch {
+	case pressed(pixelgl.KeyLeftShift), pressed(pixelgl.KeyRightShift):
+		g.shift = true
+	case released(pixelgl.KeyLeftShift), released(pixelgl.KeyRightShift):
+		g.shift = false
+	}
+
+	adjustFreq, adjustDamp := 0.0, 0.0
+
+	// Handle arrow keys to adjust frequency and damping
+	switch {
+	case released(pixelgl.KeyLeft):
+		adjustFreq = -0.1
+	case released(pixelgl.KeyRight):
+		adjustFreq = 0.1
+	case released(pixelgl.KeyUp):
+		adjustDamp = 0.1
+	case released(pixelgl.KeyDown):
+		adjustDamp = -0.1
+	case released(pixelgl.KeySpace):
+		g.showHelp = !g.showHelp
+	}
+
+	if g.shift {
+		adjustDamp *= 10
+		adjustFreq *= 10
+	}
+
+	if adjustFreq != 0 || adjustDamp != 0 {
+		g.frequency = math.Max(0, g.frequency+adjustFreq)
+		g.damping = math.Max(0, g.damping+adjustDamp)
+		g.dirty = true
+	}
+
+	if time.Now().After(g.lastClick.Add(idleTimeout)) {
+		if g.sprite != nil {
+			g.sprite.Hide()
+		}
+	}
+
+	if released(pixelgl.MouseButtonLeft) {
+		s := g.sprite
+
+		if s == nil {
+			g.sprite = NewSprite(g)
+		} else {
+			x, y := g.MousePosition()
+			s.TargetX = x
+			s.TargetY = y
+
+			switch s.State() {
+			case hiding, gone:
+				s.Show()
+			}
+		}
+
+		g.dirty = false
+		g.lastClick = time.Now()
+	}
+
+	// Sprite
+	if g.sprite != nil {
+		g.sprite.Update()
+	}
+
+	g.dirty = false
+}
+
+func (g Game) Draw(ctx *gg.Context) {
+	w, h := g.Size()
+
+	// BG
+	ctx.SetHexColor(g.bgColor)
+	ctx.DrawRectangle(0, 0, w, h)
+	ctx.Fill()
+
+	// Help text
+	if g.showHelp {
+		// For some reason our text renders upside down and backwards. Apply a
+		// matrix to fix it.
+		ctx.ScaleAbout(-1, 1, w/2, h/2)
+		ctx.RotateAbout(math.Pi, w/2, h/2)
+
+		// Instructional text
+		ctx.Push()
+		ctx.SetHexColor(g.textColor)
+		ctx.SetFontFace(g.font)
+		ctx.DrawStringAnchored("Click!", w/2, h/2, 0.5, 0.5)
+		ctx.Fill()
+		ctx.Pop()
+
+		// Status
+		str := fmt.Sprintf(
+			"Frequency: %.1f (←/→: adjust) • Damping: %.1f (↑/↓: adjust)",
+			g.frequency, g.damping,
+		)
+		ctx.Push()
+		ctx.SetHexColor(g.textColor)
+		ctx.SetFontFace(g.font)
+		ctx.DrawStringAnchored(str, w/2, h-34, 0.5, 0)
+		ctx.Fill()
+		ctx.Pop()
+
+		// Reset matrix
+		ctx.Identity()
+	}
+
+	// Draw sprites
+	if g.sprite != nil {
+		g.sprite.Draw(ctx)
+	}
+}
+
+type SpriteState int
+
+const (
+	moving SpriteState = iota
+	stopped
+	hiding
+	gone
+)
+
+type Sprite struct {
+	TargetX, TargetY, TargetRadius float64
+	X, xVel                        float64
+	Y, yVel                        float64
+	radius, radiusVel              float64
+	color                          string
+	spring                         harmonica.Spring
+	game                           *Game
+}
+
+func NewSprite(g *Game) *Sprite {
+	mouseX, mouseY := g.MousePosition()
+
+	s := &Sprite{
+		X:       mouseX,
+		Y:       mouseY,
+		TargetX: mouseX,
+		TargetY: mouseY,
+		radius:  0.1,
+		color:   g.spriteColor,
+		game:    g,
+	}
+	s.computeSpring()
+	s.randomRadius()
+
+	return s
+}
+
+func (s *Sprite) Update() {
+	if s.State() == gone {
+		return
+	}
+
+	g := s.game
+
+	if g.dirty {
+		// Recompute spring coefficients since our frequency or damping has
+		// changed.
+		s.computeSpring()
+	}
+
+	// Calculate positions based on our spring
+	s.spring.Update(&s.X, &s.xVel, s.TargetX)
+	s.spring.Update(&s.Y, &s.yVel, s.TargetY)
+	s.spring.Update(&s.radius, &s.radiusVel, s.TargetRadius)
+}
+
+func (s Sprite) Draw(ctx *gg.Context) {
+	if s.State() == gone {
+		return
+	}
+
+	ctx.Push()
+	ctx.DrawCircle(s.X, s.Y, s.radius)
+	ctx.SetHexColor(s.color)
+	ctx.Fill()
+	ctx.Pop()
+}
+
+func (s Sprite) State() SpriteState {
+	const precision = 2
+	x := roundFloat(s.X, precision)
+	tX := roundFloat(s.TargetX, precision)
+	y := roundFloat(s.Y, precision)
+	tY := roundFloat(s.TargetY, precision)
+	r := roundFloat(s.radius, precision)
+	tR := roundFloat(s.TargetRadius, precision)
+
+	if r == 0.0 {
+		return gone
+	}
+	if s.TargetRadius == 0 {
+		return hiding
+	}
+	if x == tX && y == tY && r == tR {
+		return stopped
+	}
+	return moving
+}
+
+func (s *Sprite) computeSpring() {
+	// Calculate spring coefficients
+	s.spring = harmonica.NewSpring(s.game.deltaTime, s.game.frequency, s.game.damping)
+}
+
+func (s *Sprite) randomRadius() {
+	s.TargetRadius = rand.Float64()*100.0 + 100.0
+}
+
+func (s *Sprite) Show() {
+	s.X, s.Y = s.game.MousePosition()
+	if s.radius < 0.1 {
+		s.radius = 0.1
+	}
+	s.computeSpring()
+	s.randomRadius()
+}
+
+func (s *Sprite) Hide() {
+	// Fixed frequency and damping when hiding
+	s.spring = harmonica.NewSpring(s.game.deltaTime, 3.0, 8.0)
+	s.TargetRadius = 0
+}
+
+func roundFloat(input float64, decimalPlaces int) float64 {
+	pow := math.Pow(10, float64(decimalPlaces))
+	return math.Round(pow*input) / pow
+}