diff --git a/pkg/balance/runtime.go b/pkg/balance/runtime.go
new file mode 100644
index 0000000..2864832
--- /dev/null
+++ b/pkg/balance/runtime.go
@@ -0,0 +1,29 @@
+package balance
+
+import "runtime"
+
+// Runtime environment settings.
+var Runtime rtc
+
+type rtc struct {
+	Platform platform
+	Arch     string
+}
+
+// Platform type the app was built for.
+type platform string
+
+// Runtime.Platform constants.
+const (
+	Linux   platform = "linux"
+	Windows platform = "windows"
+	Darwin  platform = "darwin"
+	Web     platform = "web"
+)
+
+func init() {
+	Runtime = rtc{
+		Platform: platform(runtime.GOOS),
+		Arch:     runtime.GOARCH,
+	}
+}
diff --git a/pkg/editor_ui.go b/pkg/editor_ui.go
index 7fcfc35..22ffe67 100644
--- a/pkg/editor_ui.go
+++ b/pkg/editor_ui.go
@@ -98,7 +98,7 @@ func NewEditorUI(d *Doodle, s *EditorScene) *EditorUI {
 		Text: "Play (P)",
 		Font: balance.PlayButtonFont,
 	}))
-	u.PlayButton.Handle(ui.Click, func(p render.Point) {
+	u.PlayButton.Handle(ui.Click, func(ed ui.EventData) {
 		u.Scene.Playtest()
 	})
 	u.Supervisor.Add(u.PlayButton)
@@ -276,6 +276,10 @@ func (u *EditorUI) Loop(ev *event.State) error {
 
 // Present the UI to the screen.
 func (u *EditorUI) Present(e render.Engine) {
+	// Draw the workspace canvas first. Rationale: we want it to have the lowest
+	// Z-index so Tooltips can pop on top of the workspace.
+	u.Workspace.Present(e, u.Workspace.Point())
+
 	// TODO: if I don't Compute() the palette window, then, whenever the dev console
 	// is open the window will blank out its contents leaving only the outermost Frame.
 	// The title bar and borders are gone. But other UI widgets don't do this.
@@ -286,7 +290,6 @@ func (u *EditorUI) Present(e render.Engine) {
 	u.MenuBar.Present(e, u.MenuBar.Point())
 	u.StatusBar.Present(e, u.StatusBar.Point())
 	u.ToolBar.Present(e, u.ToolBar.Point())
-	u.Workspace.Present(e, u.Workspace.Point())
 	u.PlayButton.Present(e, u.PlayButton.Point())
 
 	// Are we dragging a Doodad canvas?
@@ -351,7 +354,7 @@ func (u *EditorUI) SetupCanvas(d *Doodle) *uix.Canvas {
 	// Set up the drop handler for draggable doodads.
 	// NOTE: The drag event begins at editor_ui_doodad.go when configuring the
 	// Doodad Palette buttons.
-	drawing.Handle(ui.Drop, func(e render.Point) {
+	drawing.Handle(ui.Drop, func(ed ui.EventData) {
 		log.Info("Drawing canvas has received a drop!")
 		var P = ui.AbsolutePosition(drawing)
 
@@ -436,18 +439,18 @@ func (u *EditorUI) SetupMenuBar(d *Doodle) *ui.Frame {
 
 	type menuButton struct {
 		Text  string
-		Click func(render.Point)
+		Click func(ui.EventData)
 	}
 	buttons := []menuButton{
 		menuButton{
 			Text: "New Level",
-			Click: func(render.Point) {
+			Click: func(ed ui.EventData) {
 				d.GotoNewMenu()
 			},
 		},
 		menuButton{
 			Text: "New Doodad",
-			Click: func(render.Point) {
+			Click: func(ed ui.EventData) {
 				d.Prompt("Doodad size [100]>", func(answer string) {
 					size := balance.DoodadSize
 					if answer != "" {
@@ -464,7 +467,7 @@ func (u *EditorUI) SetupMenuBar(d *Doodle) *ui.Frame {
 		},
 		menuButton{
 			Text: "Save",
-			Click: func(render.Point) {
+			Click: func(ed ui.EventData) {
 				if u.Scene.filename != "" {
 					saveFunc(u.Scene.filename)
 				} else {
@@ -478,7 +481,7 @@ func (u *EditorUI) SetupMenuBar(d *Doodle) *ui.Frame {
 		},
 		menuButton{
 			Text: "Save as...",
-			Click: func(render.Point) {
+			Click: func(ed ui.EventData) {
 				d.Prompt("Save as filename>", func(answer string) {
 					if answer != "" {
 						saveFunc(answer)
@@ -488,7 +491,7 @@ func (u *EditorUI) SetupMenuBar(d *Doodle) *ui.Frame {
 		},
 		menuButton{
 			Text: "Load",
-			Click: func(render.Point) {
+			Click: func(ed ui.EventData) {
 				d.GotoLoadMenu()
 			},
 		},
diff --git a/pkg/editor_ui_doodad.go b/pkg/editor_ui_doodad.go
index 6b4046b..b8cbfcc 100644
--- a/pkg/editor_ui_doodad.go
+++ b/pkg/editor_ui_doodad.go
@@ -77,7 +77,7 @@ func (u *EditorUI) setupDoodadFrame(e render.Engine, window *ui.Window) (*ui.Fra
 			Text: "<",
 			Font: balance.MenuFont,
 		}))
-		leftBtn.Handle(ui.Click, func(p render.Point) {
+		leftBtn.Handle(ui.Click, func(ed ui.EventData) {
 			u.scrollDoodadFrame(-1)
 		})
 		u.Supervisor.Add(leftBtn)
@@ -100,7 +100,7 @@ func (u *EditorUI) setupDoodadFrame(e render.Engine, window *ui.Window) (*ui.Fra
 			Text: ">",
 			Font: balance.MenuFont,
 		}))
-		rightBtn.Handle(ui.Click, func(p render.Point) {
+		rightBtn.Handle(ui.Click, func(ed ui.EventData) {
 			u.scrollDoodadFrame(1)
 		})
 		u.Supervisor.Add(rightBtn)
@@ -179,10 +179,16 @@ func (u *EditorUI) setupDoodadFrame(e render.Engine, window *ui.Window) (*ui.Fra
 			Side: ui.W,
 		})
 
+		// Tooltip hover to show the doodad's name.
+		ui.NewTooltip(btn, ui.Tooltip{
+			Text: doodad.Title,
+			Edge: ui.Top,
+		})
+
 		// Begin the drag event to grab this Doodad.
 		// NOTE: The drag target is the EditorUI.Canvas in
 		// editor_ui.go#SetupCanvas()
-		btn.Handle(ui.MouseDown, func(e render.Point) {
+		btn.Handle(ui.MouseDown, func(ed ui.EventData) {
 			log.Warn("MouseDown on doodad %s (%s)", doodad.Filename, doodad.Title)
 			u.startDragActor(doodad, nil)
 		})
diff --git a/pkg/editor_ui_palette.go b/pkg/editor_ui_palette.go
index 5fb0a87..61b2464 100644
--- a/pkg/editor_ui_palette.go
+++ b/pkg/editor_ui_palette.go
@@ -5,7 +5,6 @@ import (
 
 	"git.kirsle.net/apps/doodle/pkg/balance"
 	"git.kirsle.net/apps/doodle/pkg/log"
-	"git.kirsle.net/go/render"
 	"git.kirsle.net/go/ui"
 )
 
@@ -54,7 +53,7 @@ func (u *EditorUI) setupPaletteFrame(window *ui.Window) *ui.Frame {
 	frame.SetBackground(balance.WindowBackground)
 
 	// Handler function for the radio buttons being clicked.
-	onClick := func(p render.Point) {
+	onClick := func(ed ui.EventData) {
 		name := u.selectedSwatch
 		swatch, ok := u.Canvas.Palette.Get(name)
 		if !ok {
@@ -95,6 +94,12 @@ func (u *EditorUI) setupPaletteFrame(window *ui.Window) *ui.Frame {
 			btn.Handle(ui.Click, onClick)
 			u.Supervisor.Add(btn)
 
+			// Add a tooltip showing the swatch attributes.
+			ui.NewTooltip(btn, ui.Tooltip{
+				Text: "Attributes: " + swatch.Attributes(),
+				Edge: ui.Left,
+			})
+
 			btn.Compute(u.d.Engine)
 			swFrame.Configure(ui.Config{
 				Height: label.Size().H,
diff --git a/pkg/editor_ui_toolbar.go b/pkg/editor_ui_toolbar.go
index de279f2..fe7ae8c 100644
--- a/pkg/editor_ui_toolbar.go
+++ b/pkg/editor_ui_toolbar.go
@@ -41,13 +41,15 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 
 	// Buttons.
 	var buttons = []struct {
-		Value string
-		Icon  string
-		Click func()
+		Value   string
+		Icon    string
+		Tooltip string
+		Click   func()
 	}{
 		{
-			Value: drawtool.PencilTool.String(),
-			Icon:  "assets/sprites/pencil-tool.png",
+			Value:   drawtool.PencilTool.String(),
+			Icon:    "assets/sprites/pencil-tool.png",
+			Tooltip: "Pencil Tool",
 			Click: func() {
 				u.Canvas.Tool = drawtool.PencilTool
 				showSwatchPalette()
@@ -56,8 +58,9 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		},
 
 		{
-			Value: drawtool.LineTool.String(),
-			Icon:  "assets/sprites/line-tool.png",
+			Value:   drawtool.LineTool.String(),
+			Icon:    "assets/sprites/line-tool.png",
+			Tooltip: "Line Tool",
 			Click: func() {
 				u.Canvas.Tool = drawtool.LineTool
 				showSwatchPalette()
@@ -66,8 +69,9 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		},
 
 		{
-			Value: drawtool.RectTool.String(),
-			Icon:  "assets/sprites/rect-tool.png",
+			Value:   drawtool.RectTool.String(),
+			Icon:    "assets/sprites/rect-tool.png",
+			Tooltip: "Rectangle Tool",
 			Click: func() {
 				u.Canvas.Tool = drawtool.RectTool
 				showSwatchPalette()
@@ -76,8 +80,9 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		},
 
 		{
-			Value: drawtool.EllipseTool.String(),
-			Icon:  "assets/sprites/ellipse-tool.png",
+			Value:   drawtool.EllipseTool.String(),
+			Icon:    "assets/sprites/ellipse-tool.png",
+			Tooltip: "Ellipse Tool",
 			Click: func() {
 				u.Canvas.Tool = drawtool.EllipseTool
 				showSwatchPalette()
@@ -86,8 +91,9 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		},
 
 		{
-			Value: drawtool.ActorTool.String(),
-			Icon:  "assets/sprites/actor-tool.png",
+			Value:   drawtool.ActorTool.String(),
+			Icon:    "assets/sprites/actor-tool.png",
+			Tooltip: "Doodad Tool\nDrag-and-drop objects into your map",
 			Click: func() {
 				u.Canvas.Tool = drawtool.ActorTool
 				showDoodadPalette()
@@ -96,8 +102,9 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		},
 
 		{
-			Value: drawtool.LinkTool.String(),
-			Icon:  "assets/sprites/link-tool.png",
+			Value:   drawtool.LinkTool.String(),
+			Icon:    "assets/sprites/link-tool.png",
+			Tooltip: "Link Tool\nConnect doodads to each other",
 			Click: func() {
 				u.Canvas.Tool = drawtool.LinkTool
 				showDoodadPalette()
@@ -106,8 +113,9 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		},
 
 		{
-			Value: drawtool.EraserTool.String(),
-			Icon:  "assets/sprites/eraser-tool.png",
+			Value:   drawtool.EraserTool.String(),
+			Icon:    "assets/sprites/eraser-tool.png",
+			Tooltip: "Eraser Tool",
 			Click: func() {
 				u.Canvas.Tool = drawtool.EraserTool
 
@@ -140,11 +148,16 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		var btnSize = btn.BoxThickness(2) + toolbarSpriteSize
 		btn.Resize(render.NewRect(btnSize, btnSize))
 
-		btn.Handle(ui.Click, func(p render.Point) {
+		btn.Handle(ui.Click, func(ed ui.EventData) {
 			button.Click()
 		})
 		u.Supervisor.Add(btn)
 
+		ui.NewTooltip(btn, ui.Tooltip{
+			Text: button.Tooltip,
+			Edge: ui.Right,
+		})
+
 		btnFrame.Pack(btn, ui.Pack{
 			Side: ui.N,
 			PadY: 2,
@@ -166,6 +179,12 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 		Side: ui.N,
 	})
 
+	ui.NewTooltip(bsLabel, ui.Tooltip{
+		Text: "Set the line thickness for drawing",
+		Edge: ui.Right,
+	})
+	u.Supervisor.Add(bsLabel)
+
 	// Brush Size widget
 	{
 		sizeFrame := ui.NewFrame("Brush Size Frame")
@@ -237,7 +256,7 @@ func (u *EditorUI) SetupToolbar(d *Doodle) *ui.Frame {
 				Text: button.Label,
 				Font: balance.SmallMonoFont,
 			}))
-			btn.Handle(ui.Click, func(p render.Point) {
+			btn.Handle(ui.Click, func(ed ui.EventData) {
 				button.F()
 			})
 			u.Supervisor.Add(btn)
diff --git a/pkg/guitest_scene.go b/pkg/guitest_scene.go
index ff1827d..c450062 100644
--- a/pkg/guitest_scene.go
+++ b/pkg/guitest_scene.go
@@ -87,7 +87,7 @@ func (s *GUITestScene) Setup(d *Doodle) error {
 			Text: label,
 			Font: balance.StatusFont,
 		}))
-		btn.Handle(ui.Click, func(p render.Point) {
+		btn.Handle(ui.Click, func(ed ui.EventData) {
 			d.Flash("%s clicked", btn)
 		})
 		s.Supervisor.Add(btn)
@@ -138,7 +138,7 @@ func (s *GUITestScene) Setup(d *Doodle) error {
 					Height:      20,
 					BorderStyle: ui.BorderRaised,
 				})
-				btn.Handle(ui.Click, func(p render.Point) {
+				btn.Handle(ui.Click, func(ed ui.EventData) {
 					d.Flash("%s clicked", btn)
 				})
 				rowFrame.Pack(btn, ui.Pack{
@@ -215,7 +215,7 @@ func (s *GUITestScene) Setup(d *Doodle) error {
 		Font: balance.StatusFont,
 	}))
 	button1.SetBackground(render.Blue)
-	button1.Handle(ui.Click, func(p render.Point) {
+	button1.Handle(ui.Click, func(ed ui.EventData) {
 		d.NewMap()
 	})
 
@@ -225,7 +225,7 @@ func (s *GUITestScene) Setup(d *Doodle) error {
 		Text: "Load Map",
 		Font: balance.StatusFont,
 	}))
-	button2.Handle(ui.Click, func(p render.Point) {
+	button2.Handle(ui.Click, func(ed ui.EventData) {
 		d.Prompt("Map name>", func(name string) {
 			d.EditDrawing(name)
 		})
diff --git a/pkg/main_scene.go b/pkg/main_scene.go
index 30ad72c..596cb61 100644
--- a/pkg/main_scene.go
+++ b/pkg/main_scene.go
@@ -85,7 +85,7 @@ func (s *MainScene) Setup(d *Doodle) error {
 			Padding:      4,
 		},
 	}))
-	s.updateButton.Handle(ui.Click, func(p render.Point) {
+	s.updateButton.Handle(ui.Click, func(ed ui.EventData) {
 		native.OpenURL(s.updateInfo.DownloadURL)
 	})
 	s.updateButton.Compute(d.Engine)
@@ -119,7 +119,7 @@ func (s *MainScene) Setup(d *Doodle) error {
 			Text: button.Name,
 			Font: balance.StatusFont,
 		}))
-		btn.Handle(ui.Click, func(p render.Point) {
+		btn.Handle(ui.Click, func(ed ui.EventData) {
 			button.Func()
 		})
 		s.Supervisor.Add(btn)
diff --git a/pkg/menu_scene.go b/pkg/menu_scene.go
index 7842f95..08ebc83 100644
--- a/pkg/menu_scene.go
+++ b/pkg/menu_scene.go
@@ -191,7 +191,7 @@ func (s *MenuScene) setupNewWindow(d *Doodle) error {
 						Font: balance.MenuFont,
 					}),
 				)
-				radio.Handle(ui.Click, func(p render.Point) {
+				radio.Handle(ui.Click, func(ed ui.EventData) {
 					s.configureCanvas(d.Engine, t.Value, s.newWallpaper)
 				})
 				s.Supervisor.Add(radio)
@@ -238,7 +238,7 @@ func (s *MenuScene) setupNewWindow(d *Doodle) error {
 					Text: t.Name,
 					Font: balance.MenuFont,
 				}))
-				radio.Handle(ui.Click, func(p render.Point) {
+				radio.Handle(ui.Click, func(ed ui.EventData) {
 					log.Info("Set wallpaper to %s", t.Value)
 					if pageType, ok := level.PageTypeFromString(s.newPageType); ok {
 						s.configureCanvas(d.Engine, pageType, t.Value)
@@ -271,9 +271,9 @@ func (s *MenuScene) setupNewWindow(d *Doodle) error {
 
 		var buttons = []struct {
 			Label string
-			F     func(render.Point)
+			F     func(ui.EventData)
 		}{
-			{"Continue", func(p render.Point) {
+			{"Continue", func(ed ui.EventData) {
 				d.Flash("Create new map with %s page type and %s wallpaper", s.newPageType, s.newWallpaper)
 				pageType, ok := level.PageTypeFromString(s.newPageType)
 				if !ok {
@@ -297,7 +297,7 @@ func (s *MenuScene) setupNewWindow(d *Doodle) error {
 				})
 			}},
 
-			{"Cancel", func(p render.Point) {
+			{"Cancel", func(ed ui.EventData) {
 				d.Goto(&MainScene{})
 			}},
 		}
@@ -371,7 +371,7 @@ func (s *MenuScene) setupLoadWindow(d *Doodle) error {
 					Text: lvl,
 					Font: balance.MenuFont,
 				}))
-				btn.Handle(ui.Click, func(p render.Point) {
+				btn.Handle(ui.Click, func(ed ui.EventData) {
 					if s.loadForPlay {
 						d.PlayLevel(lvl)
 					} else {
@@ -426,7 +426,7 @@ func (s *MenuScene) setupLoadWindow(d *Doodle) error {
 						Text: dd,
 						Font: balance.MenuFont,
 					}))
-					btn.Handle(ui.Click, func(p render.Point) {
+					btn.Handle(ui.Click, func(ed ui.EventData) {
 						d.EditFile(dd)
 					})
 					s.Supervisor.Add(btn)
@@ -467,9 +467,9 @@ func (s *MenuScene) setupLoadWindow(d *Doodle) error {
 
 		var buttons = []struct {
 			Label string
-			F     func(render.Point)
+			F     func(ui.EventData)
 		}{
-			{"Cancel", func(p render.Point) {
+			{"Cancel", func(ed ui.EventData) {
 				d.Goto(&MainScene{})
 			}},
 		}
diff --git a/pkg/play_scene.go b/pkg/play_scene.go
index a25a9dd..da4ec86 100644
--- a/pkg/play_scene.go
+++ b/pkg/play_scene.go
@@ -107,7 +107,7 @@ func (s *PlayScene) Setup(d *Doodle) error {
 		Text: "Edit (E)",
 		Font: balance.PlayButtonFont,
 	}))
-	s.editButton.Handle(ui.Click, func(p render.Point) {
+	s.editButton.Handle(ui.Click, func(ed ui.EventData) {
 		s.EditLevel()
 	})
 	s.supervisor.Add(s.editButton)
@@ -277,7 +277,7 @@ func (s *PlayScene) SetupAlertbox() {
 				Font: balance.LabelFont,
 				Text: text,
 			}))
-			btn.Handle(ui.Click, func(p render.Point) {
+			btn.Handle(ui.Click, func(ed ui.EventData) {
 				handler()
 			})
 			bottomFrame.Pack(btn, ui.Pack{