Add a CRT emulation mode

app/constants.go

@@ -20,6 +20,7 @@ const (
 	GodModeButton Control = 3
 	PauseButton   Control = 4
 	SoundButton   Control = 5
+	CrtButton     Control = 6
 	SkidMillis            = 500
 )
 
@@ -56,6 +57,7 @@ var (
 		GodModeButton: ebiten.KeyG,
 		PauseButton:   ebiten.KeyP,
 		SoundButton:   ebiten.KeyS,
+		CrtButton:     ebiten.KeyC,
 	}
 
 	White = color.RGBA{

app/crt.go

@@ -0,0 +1,57 @@
+// A Kage port of https://www.shadertoy.com/view/Ms23DR
+//
+// The original license comment is:
+//	Loosely based on postprocessing shader by inigo quilez,
+//	License Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
+//	https://creativecommons.org/licenses/by-nc-sa/3.0/deed.en
+
+//go:build ignore
+
+package app
+
+//kage:unit pixels
+
+func curve(uv vec2) vec2 {
+	uv = (uv - 0.5) * 2
+	uv *= 1.08
+	uv.x *= (1 + pow((abs(uv.y)/8), 2))
+	uv.y *= (1 + pow((abs(uv.x)/6), 2))
+	uv = uv/2 + 0.5
+	uv = uv*0.92 + 0.04
+
+	return uv
+}
+
+func Fragment(dst vec4, src vec2, color vec4) vec4 {
+	origin, size := imageSrcRegionOnTexture()
+	q := (src - origin) / size
+	uv := q
+	uv = curve(uv)
+
+	var col vec3
+	col.r = imageSrc0At(vec2(uv.x+0.001, uv.y+0.001)*size+origin).x + 0.05
+	col.g = imageSrc0At(vec2(uv.x+0.000, uv.y-0.002)*size+origin).y + 0.05
+	col.b = imageSrc0At(vec2(uv.x-0.002, uv.y+0.000)*size+origin).z + 0.05
+	col.r += 0.08 * imageSrc0At((0.75*vec2(0.025, -0.027)+vec2(uv.x+0.001, uv.y+0.001))*size+origin).x
+	col.g += 0.05 * imageSrc0At((0.75*vec2(-0.022, -0.02)+vec2(uv.x+0.000, uv.y-0.002))*size+origin).y
+	col.b += 0.08 * imageSrc0At((0.75*vec2(-0.02, -0.018)+vec2(uv.x-0.002, uv.y+0.000))*size+origin).z
+
+	col = clamp(col*0.6+0.4*col*col, 0, 1)
+
+	vig := (16.0 * uv.x * uv.y * (1 - uv.x) * (1 - uv.y))
+	col *= vec3(pow(vig, 0.3))
+	col *= vec3(0.95, 1.05, 0.95)
+	col *= 2.8
+
+	scans := clamp(0.35+0.35*sin(uv.y*size.y*1.5), 0, 1)
+	s := pow(scans, 1.7)
+	col *= vec3(0.4 + 0.7*s)
+
+	if uv.x < 0.0 || uv.x > 1.0 || uv.y < 0 || uv.y > 1 {
+		col *= 0
+	}
+
+	col *= (1 - 0.35*vec3(clamp((mod(src.x, 2)-1)*2, 0, 1)))
+
+	return vec4(col, 1)
+}

entity/types.go

@@ -17,6 +17,7 @@ type GameState struct {
 	Keys      map[app.Control]bool
 	GodMode   bool
 	SoundOn   bool
+	CrtOn     bool
 	Pause     bool
 	Debug     string
 	Sounds    audio.GameSounds

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	_ "embed"
 	"errors"
 	"fmt"
 	"github.com/depsypher/gojoust/app"
@@ -16,6 +17,9 @@ import (
 
 var (
 	ss *entity.Sheet
+
+	//go:embed app/crt.go
+	crt_go []byte
 )
 
 func init() {
@@ -32,6 +36,8 @@ type Game struct {
 	inited bool
 	ss     entity.Sheet
 	state  *entity.GameState
+	screen *ebiten.Image
+	crt    *ebiten.Shader
 }
 
 func (g *Game) init() {
@@ -41,6 +47,7 @@ func (g *Game) init() {
 			Keys:      make(map[app.Control]bool),
 			GodMode:   false,
 			SoundOn:   true,
+			CrtOn:     true,
 			WaveStart: time.Now(),
 		}
 
@@ -65,6 +72,12 @@ func (g *Game) init() {
 			errSound := errors.New("error loading sounds")
 			log.Fatal(errors.Join(errSound, err))
 		}
+
+		s, err := ebiten.NewShader(crt_go)
+		if err != nil {
+			return
+		}
+		g.crt = s
 	}()
 }
 
@@ -87,6 +100,10 @@ func (g *Game) Update() error {
 		g.state.Keys[app.SoundButton] = true
 		g.state.SoundOn = !g.state.SoundOn
 	})
+	toggle(app.CrtButton, g.state.Keys, func() {
+		g.state.Keys[app.CrtButton] = true
+		g.state.CrtOn = !g.state.CrtOn
+	})
 
 	if time.Now().After(g.state.WaveStart.Add(time.Duration(3) * time.Second)) {
 		if len(g.state.Buzzards) < 3 && time.Now().After(g.state.NextSpawn) {
@@ -112,24 +129,40 @@ func (g *Game) Update() error {
 }
 
 func (g *Game) Draw(screen *ebiten.Image) {
+	w, h := screen.Bounds().Dx(), screen.Bounds().Dy()
+	if g.screen == nil {
+		g.screen = ebiten.NewImage(w, h)
+	} else {
+		g.screen.Clear()
+	}
+
 	if g.state.GodMode {
-		ebitenutil.DebugPrint(screen, fmt.Sprintf("FPS: %3.2f\nTPS: %3.2f", ebiten.ActualFPS(), ebiten.ActualTPS()))
-		ebitenutil.DebugPrintAt(screen, g.state.Debug, 70, 0)
-		ebitenutil.DebugPrintAt(screen, fmt.Sprintf("%f", g.state.Player.Y), 70, 20)
+		ebitenutil.DebugPrint(g.screen, fmt.Sprintf("FPS: %3.2f\nTPS: %3.2f", ebiten.ActualFPS(), ebiten.ActualTPS()))
+		ebitenutil.DebugPrintAt(g.screen, g.state.Debug, 70, 0)
+		ebitenutil.DebugPrintAt(g.screen, fmt.Sprintf("%f", g.state.Player.Y), 70, 20)
 
 		for _, lane := range app.Lanes {
 			y := float32(lane)
-			vector.StrokeLine(screen, 0, y, app.ScreenWidth, y, 1, app.Yellow, false)
+			vector.StrokeLine(g.screen, 0, y, app.ScreenWidth, y, 1, app.Yellow, false)
 		}
 	}
 	for _, cliff := range g.state.Cliffs {
-		cliff.Sprite.DrawSprite(screen)
+		cliff.Sprite.DrawSprite(g.screen)
 	}
 	for _, b := range g.state.Buzzards {
-		b.Draw(screen)
+		b.Draw(g.screen)
 	}
 
-	g.state.Player.Draw(screen)
+	g.state.Player.Draw(g.screen)
+
+	if g.state.CrtOn {
+		op := &ebiten.DrawRectShaderOptions{}
+		op.Images[0] = g.screen
+		screen.DrawRectShader(w, h, g.crt, op)
+	} else {
+		op := &ebiten.DrawImageOptions{}
+		screen.DrawImage(g.screen, op)
+	}
 }
 
 func (g *Game) Layout(outsideWidth, outsideHeight int) (int, int) {