diff --git a/internal/game/imgui.go b/internal/game/imgui.go
index 1bcae21..7ceb1c6 100644
--- a/internal/game/imgui.go
+++ b/internal/game/imgui.go
@@ -1,7 +1,6 @@
 package game
 
 import (
-	"fmt"
 	"log"
 	"math"
 	"os"
@@ -9,6 +8,8 @@ import (
 
 	"edgaru089.ml/go/gl01/internal/asset"
 	"edgaru089.ml/go/gl01/internal/igwrap"
+	"edgaru089.ml/go/gl01/internal/igwrap/backend"
+	"edgaru089.ml/go/gl01/internal/io"
 	"edgaru089.ml/go/gl01/internal/util/itype"
 	"edgaru089.ml/go/gl01/internal/world"
 	"github.com/go-gl/glfw/v3.3/glfw"
@@ -19,6 +20,8 @@ type guiState struct {
 	showLog, showDebugInfo bool
 	logFollow              bool
 
+	lastframeCgoCalls int64
+
 	loadChunkFile string
 	loadChunkID   [2]int32
 
@@ -35,7 +38,7 @@ func (g *Game) initImgui(win *glfw.Window) {
 	cfg.SetOversampleV(1)
 	cfg.SetPixelSnapH(true)
 	g.io.Fonts().AddFontFromMemoryTTFV(asset.Unifont, 16, cfg, g.io.Fonts().GlyphRangesChineseFull())
-	igwrap.Init(win)
+	backend.Init(win)
 
 	g.gui = guiState{
 		showLog:       true,
@@ -49,6 +52,19 @@ func (g *Game) initImgui(win *glfw.Window) {
 }
 
 func (g *Game) imgui() {
+	if io.ShowDebugInfo {
+		imgui.SetNextWindowPosV(imgui.Vec2{}, imgui.ConditionAlways, imgui.Vec2{})
+		if igwrap.Begin("F3", nil, imgui.WindowFlagsAlwaysAutoResize|imgui.WindowFlagsNoBackground|imgui.WindowFlagsNoNavFocus|imgui.WindowFlagsNoDecoration|imgui.WindowFlagsNoInputs|imgui.WindowFlagsNoSavedSettings|imgui.WindowFlagsNoFocusOnAppearing) {
+			igwrap.Text("Gl01(glfw%s, imgui%s) - compiled by %s[%s/%s]", glfw.GetVersionString(), imgui.Version(), runtime.Version(), runtime.GOOS, runtime.GOARCH)
+			igwrap.Text("CgoCalls:%d (%d lastframe), Goroutines:%d", runtime.NumCgoCall(), runtime.NumCgoCall()-g.gui.lastframeCgoCalls, runtime.NumGoroutine())
+			imgui.Text("")
+
+			pos := g.player.Position()
+			igwrap.Text("Player: (%.3f, %.5f, %.3f) - (Y%.2f, Z%.2f)", pos[0], pos[1], pos[2], g.rotY.Degrees(), g.rotZ)
+			imgui.End()
+		}
+	}
+	g.gui.lastframeCgoCalls = runtime.NumCgoCall()
 
 	if imgui.BeginV("Player", nil, imgui.WindowFlagsAlwaysAutoResize) {
 		pos := g.player.Position()
@@ -58,17 +74,6 @@ func (g *Game) imgui() {
 	}
 	imgui.End()
 
-	if imgui.BeginV("Go Runtime", nil, imgui.WindowFlagsAlwaysAutoResize) {
-		imgui.Text(fmt.Sprintf("%s/%s, compiler: %s", runtime.GOOS, runtime.GOARCH, runtime.Compiler))
-		imgui.Text(fmt.Sprintf("NumCPU=%d, NumGOMAXPROCS=%d", runtime.NumCPU(), runtime.GOMAXPROCS(0)))
-		imgui.Text(fmt.Sprintf("NumCgoCalls=%d, NumGoroutine=%d", runtime.NumCgoCall(), runtime.NumGoroutine()))
-		imgui.Spacing()
-		if imgui.ButtonV("!!! PANIC !!!", imgui.Vec2{X: -2, Y: 0}) {
-			panic("Manual Panic")
-		}
-	}
-	imgui.End()
-
 	if igwrap.Begin("Logs", &g.gui.showLog, imgui.WindowFlagsMenuBar) {
 		if imgui.BeginMenuBar() {
 			if imgui.Button("Clear") {
diff --git a/internal/game/logic.go b/internal/game/logic.go
index fe600d0..4059ada 100644
--- a/internal/game/logic.go
+++ b/internal/game/logic.go
@@ -6,7 +6,7 @@ import (
 	"os"
 	"time"
 
-	"edgaru089.ml/go/gl01/internal/igwrap"
+	"edgaru089.ml/go/gl01/internal/igwrap/backend"
 	"edgaru089.ml/go/gl01/internal/io"
 	"edgaru089.ml/go/gl01/internal/render"
 	"edgaru089.ml/go/gl01/internal/util/itype"
@@ -105,13 +105,13 @@ func (g *Game) Init(win *glfw.Window) {
 
 	win.SetMouseButtonCallback(func(w *glfw.Window, button glfw.MouseButton, action glfw.Action, mods glfw.ModifierKey) {
 		if g.paused {
-			igwrap.MouseButtonCallback(button, action)
+			backend.MouseButtonCallback(button, action)
 		}
 	})
 
 	win.SetKeyCallback(func(w *glfw.Window, key glfw.Key, scancode int, action glfw.Action, mods glfw.ModifierKey) {
 		if g.paused {
-			igwrap.KeyCallback(key, action)
+			backend.KeyCallback(key, action)
 		}
 		if action == glfw.Press {
 			if g.paused {
@@ -157,13 +157,13 @@ func (g *Game) Init(win *glfw.Window) {
 
 	win.SetCharCallback(func(w *glfw.Window, char rune) {
 		if g.paused {
-			igwrap.InputCallback(char)
+			backend.InputCallback(char)
 		}
 	})
 
 	win.SetScrollCallback(func(w *glfw.Window, xpos, ypos float64) {
 		if g.paused {
-			igwrap.MouseScrollCallback(xpos, ypos)
+			backend.MouseScrollCallback(xpos, ypos)
 		}
 	})
 
@@ -173,7 +173,7 @@ const airAccel = 0.1
 
 // Update updates the game state, not necessarily in the main thread.
 func (g *Game) Update(win *glfw.Window, delta time.Duration) {
-	igwrap.NewFrame()
+	backend.NewFrame()
 	imgui.ShowDemoWindow(nil)
 
 	if !g.paused {
@@ -251,5 +251,5 @@ func (g *Game) Render(win *glfw.Window) {
 	g.worldrender.Render(g.world, g.view)
 	render.Framewire.Render(g.view)
 
-	igwrap.Render(win)
+	backend.Render(win)
 }
diff --git a/internal/igwrap/glfw.go b/internal/igwrap/backend/glfw.go
similarity index 99%
rename from internal/igwrap/glfw.go
rename to internal/igwrap/backend/glfw.go
index e843d86..d5887cb 100644
--- a/internal/igwrap/glfw.go
+++ b/internal/igwrap/backend/glfw.go
@@ -1,4 +1,4 @@
-package igwrap
+package backend
 
 import (
 	"time"
diff --git a/internal/igwrap/glyph_ranges.go b/internal/igwrap/backend/glyph_ranges.go
similarity index 96%
rename from internal/igwrap/glyph_ranges.go
rename to internal/igwrap/backend/glyph_ranges.go
index 0a6438d..0d7f706 100644
--- a/internal/igwrap/glyph_ranges.go
+++ b/internal/igwrap/backend/glyph_ranges.go
@@ -1,4 +1,4 @@
-package igwrap
+package backend
 
 import "github.com/inkyblackness/imgui-go/v4"
 
diff --git a/internal/igwrap/render.go b/internal/igwrap/backend/render.go
similarity index 97%
rename from internal/igwrap/render.go
rename to internal/igwrap/backend/render.go
index f59c7e9..32cc476 100644
--- a/internal/igwrap/render.go
+++ b/internal/igwrap/backend/render.go
@@ -1,8 +1,9 @@
-package igwrap
+package backend
 
 import (
 	_ "embed"
 
+	"edgaru089.ml/go/gl01/internal/igwrap"
 	"edgaru089.ml/go/gl01/internal/render"
 	"github.com/go-gl/gl/all-core/gl"
 	"github.com/go-gl/glfw/v3.3/glfw"
@@ -86,6 +87,7 @@ func CreateFontsTexture() {
 	)
 
 	io.Fonts().SetTextureID(imgui.TextureID(tex))
+	igwrap.SetTextureFlag(tex, igwrap.TextureFlag_Red)
 
 	gl.BindTexture(gl.TEXTURE_2D, uint32(lastTexture))
 }
@@ -202,6 +204,7 @@ func Render(win *glfw.Window) {
 			if cmd.HasUserCallback() {
 				cmd.CallUserCallback(list)
 			} else {
+				shader.SetUniformInt("flags", int32(igwrap.GetTextureFlag(uint32(cmd.TextureID()))))
 				gl.BindTexture(gl.TEXTURE_2D, uint32(cmd.TextureID()))
 				clipRect := cmd.ClipRect()
 				gl.Scissor(int32(clipRect.X), int32(fbHeight)-int32(clipRect.W), int32(clipRect.Z-clipRect.X), int32(clipRect.W-clipRect.Y))
diff --git a/internal/igwrap/backend/shader.frag b/internal/igwrap/backend/shader.frag
new file mode 100644
index 0000000..12adf13
--- /dev/null
+++ b/internal/igwrap/backend/shader.frag
@@ -0,0 +1,33 @@
+#version 330
+
+#define FLAG_RED    (1<<0)
+#define FLAG_GREEN  (1<<1)
+#define FLAG_BLUE   (1<<2)
+#define FLAG_ALPHA  (1<<3)
+#define FLAG_COLORS (FLAG_RED | FLAG_GREEN | FLAG_BLUE | FLAG_ALPHA)
+
+#define FLAG_LINEAR (1<<4)
+
+uniform sampler2D tex;
+uniform int flags;
+
+in vec2 fragUV;
+in vec4 fragColor;
+
+out vec4 outputColor;
+
+const float gamma = 2.2;
+
+void main() {
+	if ((flags & FLAG_COLORS) == FLAG_RED) {
+		outputColor = vec4(fragColor.rgb, fragColor.a * texture(tex, fragUV.st).r);
+	} else {
+		vec4 color = texture(tex, fragUV.st);
+		if ((flags & FLAG_LINEAR) != 0)
+			color.rgb = pow(color.rgb, vec3(1.0/gamma));
+		outputColor = color * fragColor;
+		if ((flags & FLAG_ALPHA) == 0)
+			outputColor.a = 1;
+	}
+}
+
diff --git a/internal/igwrap/shader.vert b/internal/igwrap/backend/shader.vert
similarity index 100%
rename from internal/igwrap/shader.vert
rename to internal/igwrap/backend/shader.vert
diff --git a/internal/igwrap/color.go b/internal/igwrap/color.go
deleted file mode 100644
index 13b433b..0000000
--- a/internal/igwrap/color.go
+++ /dev/null
@@ -1,13 +0,0 @@
-package igwrap
-
-import "github.com/inkyblackness/imgui-go/v4"
-
-// Color converts non-premultiplied RGBA color into imgui.Vec4.
-func Color(r, g, b, a uint8) imgui.Vec4 {
-	return imgui.Vec4{
-		X: float32(r) / 255,
-		Y: float32(g) / 255,
-		Z: float32(b) / 255,
-		W: float32(a) / 255,
-	}
-}
diff --git a/internal/igwrap/convert.go b/internal/igwrap/convert.go
new file mode 100644
index 0000000..9bc6725
--- /dev/null
+++ b/internal/igwrap/convert.go
@@ -0,0 +1,26 @@
+package igwrap
+
+import (
+	"edgaru089.ml/go/gl01/internal/util/itype"
+	"github.com/inkyblackness/imgui-go/v4"
+)
+
+// Color converts non-premultiplied RGBA color into imgui.Vec4.
+func Color(r, g, b, a uint8) imgui.Vec4 {
+	return imgui.Vec4{
+		X: float32(r) / 255,
+		Y: float32(g) / 255,
+		Z: float32(b) / 255,
+		W: float32(a) / 255,
+	}
+}
+
+// Vec2 converts itype.Vec2f to imgui.Vec2.
+func Vec2(v itype.Vec2f) imgui.Vec2 {
+	return imgui.Vec2{X: v[0], Y: v[1]}
+}
+
+// Vec4 converts itype.Vec4f to imgui.Vec4.
+func Vec4(v itype.Vec4f) imgui.Vec4 {
+	return imgui.Vec4{X: v[0], Y: v[1], Z: v[2], W: v[3]}
+}
diff --git a/internal/igwrap/imagewrap.go b/internal/igwrap/imagewrap.go
new file mode 100644
index 0000000..3a4708b
--- /dev/null
+++ b/internal/igwrap/imagewrap.go
@@ -0,0 +1,77 @@
+package igwrap
+
+import (
+	"sync"
+
+	"edgaru089.ml/go/gl01/internal/util/itype"
+	"github.com/inkyblackness/imgui-go/v4"
+)
+
+// Image creates a ImGUI image based on the given texture.
+// For *render.Texture, use tex.Handle().
+//
+// size is in pixels. texRange is in [0, 1].
+func Image(tex uint32, size itype.Vec2f, texRange itype.Rectf) {
+	min, max := texRange.MinPoint(), texRange.MaxPoint()
+	imgui.ImageV(
+		imgui.TextureID(tex),
+		Vec2(size),
+		imgui.Vec2{X: min[0], Y: max[1]},
+		imgui.Vec2{X: max[0], Y: min[1]},
+		Color(255, 255, 255, 255),
+		imgui.Vec4{},
+	)
+}
+
+// ImageV creates a ImGUI image based on the given texture.
+// For *render.Texture, use tex.Handle().
+//
+// size is in pixels. texRange is in [0, 1].
+func ImageV(tex uint32, size itype.Vec2f, texRange itype.Rectf, texColor itype.Vec4f, borderColor itype.Vec4f) {
+	imgui.ImageV(
+		imgui.TextureID(tex),
+		Vec2(size),
+		Vec2(texRange.MinPoint()),
+		Vec2(texRange.MaxPoint()),
+		Vec4(texColor),
+		Vec4(borderColor),
+	)
+}
+
+type TextureFlag int
+
+const (
+	TextureFlag_Red   TextureFlag = 1 << iota // Renders the Red channel.
+	TextureFlag_Green                         // Renders the Green channel.
+	TextureFlag_Blue                          // Renders the Blue channel.
+	TextureFlag_Alpha                         // Renders the Alpha channel.
+
+	TextureFlag_Linear // Linear source data, requires gamma correction.
+
+	TextureFlag_RGB  = TextureFlag_Red | TextureFlag_Green | TextureFlag_Blue
+	TextureFlag_RGBA = TextureFlag_Red | TextureFlag_Green | TextureFlag_Blue | TextureFlag_Alpha
+)
+
+var (
+	texflags     map[uint32]TextureFlag = make(map[uint32]TextureFlag)
+	texflagslock sync.RWMutex
+)
+
+// SetTextureFlag changes the flag of a texture to the given flags combined.
+func SetTextureFlag(tex uint32, flags ...TextureFlag) {
+	var f TextureFlag
+	for _, f0 := range flags {
+		f |= f0
+	}
+
+	texflagslock.Lock()
+	defer texflagslock.Unlock()
+	texflags[tex] = f
+}
+
+// TextureFlag returns the flags of a given texture.
+func GetTextureFlag(tex uint32) TextureFlag {
+	texflagslock.RLock()
+	defer texflagslock.RUnlock()
+	return texflags[tex]
+}
diff --git a/internal/igwrap/shader.frag b/internal/igwrap/shader.frag
deleted file mode 100644
index 7500784..0000000
--- a/internal/igwrap/shader.frag
+++ /dev/null
@@ -1,13 +0,0 @@
-#version 330
-
-uniform sampler2D tex;
-
-in vec2 fragUV;
-in vec4 fragColor;
-
-out vec4 outputColor;
-
-void main() {
-    outputColor = vec4(fragColor.rgb, fragColor.a * texture(tex, fragUV.st).r);
-}
-
diff --git a/internal/igwrap/wrap.go b/internal/igwrap/wrap.go
index 24a4286..bbfc152 100644
--- a/internal/igwrap/wrap.go
+++ b/internal/igwrap/wrap.go
@@ -28,7 +28,7 @@ func Text(format string, a ...interface{}) {
 // returns true.
 func Begin(id string, open *bool, flags imgui.WindowFlags) bool {
 	// skip if the window is not open
-	if !(*open) {
+	if open != nil && !(*open) {
 		return false
 	}
 
diff --git a/internal/util/itype/vec.go b/internal/util/itype/vec.go
index d108b4f..44f5a5d 100644
--- a/internal/util/itype/vec.go
+++ b/internal/util/itype/vec.go
@@ -61,6 +61,10 @@ func (v Vec2f) Addv(x, y float32) Vec2f {
 	return Vec2f{v[0] + x, v[1] + y}
 }
 
+func (v Vec2f) Multiply(x float32) Vec2f {
+	return Vec2f{v[0] * x, v[1] * x}
+}
+
 func (v Vec2f) Floor() Vec2i {
 	return Vec2i{
 		int(math.Floor(float64(v[0]))),