diff --git a/src/device/input/button/v01.go b/src/device/input/button/v01.go
index dcd0f1e..61c6843 100644
--- a/src/device/input/button/v01.go
+++ b/src/device/input/button/v01.go
@@ -30,20 +30,10 @@ type (
 			Message string
 		}
 		Players []struct {
-			Buttons struct {
-				Up    string
-				Down  string
-				Left  string
-				Right string
-				L     string
-				R     string
-				A     string
-				B     string
-				X     string
-				Y     string
-			}
+			Transformation v01Transformation
 		}
 	}
+	v01Transformation map[string]string
 )
 
 func NewV01(src raw.Raw) V01 {
@@ -67,7 +57,33 @@ func (v01 V01) Read() []Button {
 		log.Printf("%v: %s", err, line)
 	}
 	v01.telemetry(msg)
-	return msg.buttons()
+
+	return v01.cfg.transform(msg).buttons()
+}
+
+func (cfg v01Cfg) transform(msg v01Msg) v01Msg {
+	if len(cfg.Players) == 0 {
+		return msg
+	}
+	user := cfg.Users[msg.U]
+	if user.Player < 1 {
+		msg.Y = ""
+		msg.N = ""
+		return msg
+	}
+	player := cfg.Players[user.Player-1]
+	msg.Y = player.Transformation.pipe(msg.Y)
+	msg.N = player.Transformation.pipe(msg.N)
+	return msg
+}
+
+func (t v01Transformation) pipe(s string) string {
+	for i := range s {
+		if v := t[s[i:i+1]]; v != "" {
+			s = s[:i] + v[:1] + s[i+1:]
+		}
+	}
+	return s
 }
 
 func (v01 V01) telemetry(msg v01Msg) {
diff --git a/src/device/input/button/v01_exported_test.go b/src/device/input/button/v01_exported_test.go
new file mode 100644
index 0000000..455a3b1
--- /dev/null
+++ b/src/device/input/button/v01_exported_test.go
@@ -0,0 +1,31 @@
+package button_test
+
+import (
+	"fmt"
+	"mayhem-party/src/device/input/button"
+	"testing"
+	"time"
+)
+
+func TestV01(t *testing.T) {
+	src := constSrc(fmt.Sprintf(`{"T":%v,"U":"bel","Y":"abc","N":"cde"}`, time.Now().UnixNano()/int64(time.Millisecond)-50))
+	t.Logf("(%v) %s", len(src), src.Read())
+	v01 := button.NewV01(src)
+	got := v01.Read()
+	want := []button.Button{
+		{Down: true, Char: 'a'},
+		{Down: true, Char: 'b'},
+		{Down: true, Char: 'c'},
+		{Down: false, Char: 'c'},
+		{Down: false, Char: 'd'},
+		{Down: false, Char: 'e'},
+	}
+	if len(got) != len(want) {
+		t.Fatal(len(want), len(got))
+	}
+	for i := range got {
+		if got[i] != want[i] {
+			t.Errorf("[%d] want %+v got %+v", i, want[i], got[i])
+		}
+	}
+}
diff --git a/src/device/input/button/v01_test.go b/src/device/input/button/v01_test.go
index 455a3b1..8cf335f 100644
--- a/src/device/input/button/v01_test.go
+++ b/src/device/input/button/v01_test.go
@@ -1,31 +1,51 @@
-package button_test
+package button
 
 import (
-	"fmt"
-	"mayhem-party/src/device/input/button"
 	"testing"
-	"time"
 )
 
-func TestV01(t *testing.T) {
-	src := constSrc(fmt.Sprintf(`{"T":%v,"U":"bel","Y":"abc","N":"cde"}`, time.Now().UnixNano()/int64(time.Millisecond)-50))
-	t.Logf("(%v) %s", len(src), src.Read())
-	v01 := button.NewV01(src)
-	got := v01.Read()
-	want := []button.Button{
-		{Down: true, Char: 'a'},
-		{Down: true, Char: 'b'},
-		{Down: true, Char: 'c'},
-		{Down: false, Char: 'c'},
-		{Down: false, Char: 'd'},
-		{Down: false, Char: 'e'},
+func TestV01TransformationPipe(t *testing.T) {
+	cases := map[string]struct {
+		input string
+		xform map[string]string
+		want  string
+	}{
+		"empty input": {
+			xform: map[string]string{"a": "bc"},
+		},
+		"empty xform": {
+			input: "aa",
+			want:  "aa",
+		},
+		"all": {
+			input: "aa",
+			xform: map[string]string{"a": "cc"},
+			want:  "cc",
+		},
+		"last": {
+			input: "ba",
+			xform: map[string]string{"a": "cc"},
+			want:  "bc",
+		},
+		"first": {
+			input: "ab",
+			xform: map[string]string{"a": "cc"},
+			want:  "cb",
+		},
+		"noop": {
+			input: "bb",
+			xform: map[string]string{"a": "bc"},
+			want:  "bb",
+		},
 	}
-	if len(got) != len(want) {
-		t.Fatal(len(want), len(got))
-	}
-	for i := range got {
-		if got[i] != want[i] {
-			t.Errorf("[%d] want %+v got %+v", i, want[i], got[i])
-		}
+
+	for name, d := range cases {
+		c := d
+		t.Run(name, func(t *testing.T) {
+			got := v01Transformation(c.xform).pipe(c.input)
+			if got != c.want {
+				t.Errorf("%+v(%s) want %s got %s", c.xform, c.input, c.want, got)
+			}
+		})
 	}
 }