diff --git a/internal/cops/display/terminal.go b/internal/cops/display/terminal.go
index 3937b91..cfef86b 100644
--- a/internal/cops/display/terminal.go
+++ b/internal/cops/display/terminal.go
@@ -2,6 +2,7 @@ package display
 
 import (
 	"io"
+	"log"
 	"os"
 
 	"github.com/borkshop/bork/internal/cops/terminal"
@@ -11,22 +12,22 @@ import (
 type Terminal struct {
 	*Display
 
-	out   *os.File
-	term  terminal.Terminal
-	model ColorModel
-	buf   []byte
-	cur   Cursor
+	ColorModel ColorModel
+	out        *os.File
+	term       terminal.Terminal
+	buf        []byte
+	cur        Cursor
 }
 
 // NewTerminal takes control of a terminal, readying it for rendering by
 // putting it in raw mode, clearing it, and hiding the cursor.
 func NewTerminal(out *os.File) (*Terminal, error) {
 	term := &Terminal{
-		out:   out,
-		term:  terminal.New(out.Fd()),
-		model: Model24, // TODO #choices
-		buf:   make([]byte, 0, 65536),
-		cur:   Start,
+		out:        out,
+		term:       terminal.New(out.Fd()),
+		ColorModel: Model24, // TODO #choices
+		buf:        make([]byte, 0, 65536),
+		cur:        Start,
 	}
 	return term, term.open()
 }
@@ -74,10 +75,12 @@ func (term *Terminal) flush() error {
 	}
 	attempts := 5 // TODO sanity check: is this even worthwhile?
 	n, err := term.out.Write(term.buf)
+	log.Printf("display.Terminal flushed %q", term.buf[:n])
 	for attempts > 1 && err == io.ErrShortWrite {
 		attempts--
 		term.buf = term.buf[:copy(term.buf, term.buf[n:])]
 		n, err = term.out.Write(term.buf)
+		log.Printf("display.Terminal flushed %q", term.buf[:n])
 	}
 	term.buf = term.buf[:0]
 	return err
@@ -96,7 +99,7 @@ func (term *Terminal) UpdateSize() error {
 }
 
 func (term Terminal) fullRender(cur Cursor, buf []byte) ([]byte, Cursor) {
-	return Render(buf, cur, term.Display, term.model)
+	return Render(buf, cur, term.Display, term.ColorModel)
 }
 
 // Render the display buffer to the terminal.
diff --git a/proofs/testpattern/main.go b/proofs/testpattern/main.go
new file mode 100644
index 0000000..d7609c6
--- /dev/null
+++ b/proofs/testpattern/main.go
@@ -0,0 +1,148 @@
+package main
+
+import (
+	"fmt"
+	"image/color"
+	"log"
+	"os"
+	"os/signal"
+	"strconv"
+	"syscall"
+
+	"github.com/borkshop/bork/internal/cops/display"
+	"github.com/borkshop/bork/internal/input"
+)
+
+func colorGB(x, y int) (f, b color.RGBA) {
+	f.A = 0xff
+	b.A = 0xff
+	f.G += uint8(y)
+	b.B += uint8(x)
+	return f, b
+}
+
+func colorEights(x, y int) (f, b color.RGBA) {
+	return display.Colors[y%8], display.Colors[x%8]
+}
+
+type xyColorFunc func(x, y int) (f, b color.RGBA)
+
+func fgOnly(cf xyColorFunc) xyColorFunc {
+	return func(x, y int) (f, b color.RGBA) {
+		f, _ = cf(x, y)
+		b = display.Colors[0]
+		return f, b
+	}
+}
+
+func bgOnly(cf xyColorFunc) xyColorFunc {
+	return func(x, y int) (f, b color.RGBA) {
+		_, b = cf(x, y)
+		f = display.Colors[7]
+		return f, b
+	}
+}
+
+func run() (rerr error) {
+	f, err := os.Create("debug.log")
+	if err != nil {
+		return err
+	}
+	log.SetOutput(f)
+
+	term, err := display.NewTerminal(os.Stdout)
+	if err != nil {
+		return err
+	}
+	defer func() {
+		if cerr := term.Close(); rerr == nil {
+			rerr = cerr
+		}
+	}()
+
+	commands, mute := input.Channel(os.Stdin)
+	defer mute()
+
+	sigwinch := make(chan os.Signal)
+	signal.Notify(sigwinch, syscall.SIGWINCH)
+
+	var colorFunc xyColorFunc = colorGB
+
+	for {
+		sz := term.Display.Rect.Size()
+		for y := 0; y < sz.Y; y++ {
+			for x := 0; x < sz.X; x++ {
+				t := strconv.Itoa(y % 10)
+				f, b := colorFunc(x, y)
+				term.Display.SetRGBA(x, y, t, f, b)
+				// term.Display.Set(x, y, t, nil, nil)
+			}
+		}
+
+		if err := term.Render(); err != nil {
+			return err
+		}
+
+		select {
+		case <-sigwinch:
+			if err := term.UpdateSize(); err != nil {
+				return err
+			}
+			log.Printf("display resized to %v", term.Bounds())
+
+		case command := <-commands:
+			switch c := command.(type) {
+			case rune:
+				switch c {
+				case 'q':
+					colorFunc = colorEights
+					log.Printf("using colorFunc = colorEights")
+				case 'w':
+					colorFunc = colorGB
+					log.Printf("using colorFunc = colorGB")
+				case 'a':
+					colorFunc = fgOnly(colorEights)
+					log.Printf("using colorFunc = fgOnly(colorEights)")
+				case 's':
+					colorFunc = fgOnly(colorGB)
+					log.Printf("using colorFunc = fgOnly(colorGB)")
+				case 'z':
+					colorFunc = bgOnly(colorEights)
+					log.Printf("using colorFunc = bgOnly(colorEights)")
+				case 'x':
+					colorFunc = bgOnly(colorGB)
+					log.Printf("using colorFunc = bgOnly(colorGB)")
+
+				case '1':
+					term.ColorModel = display.Model0
+					log.Printf("using ColorModel = Model0")
+				case '2':
+					term.ColorModel = display.Model3
+					log.Printf("using ColorModel = Model3")
+				case '3':
+					term.ColorModel = display.Model4
+					log.Printf("using ColorModel = Model4")
+				case '4':
+					term.ColorModel = display.Model8
+					log.Printf("using ColorModel = Model8")
+				case '5':
+					term.ColorModel = display.Model24
+					log.Printf("using ColorModel = Model24")
+				case '6':
+					term.ColorModel = display.ModelCompat24
+					log.Printf("using ColorModel = ModelCompat24")
+
+				case '', '':
+					return nil
+				}
+			}
+		}
+
+	}
+}
+
+func main() {
+	if err := run(); err != nil {
+		fmt.Printf("%v\n", err)
+	}
+}