diff --git a/docs/UI_DESIGN.md b/docs/UI_DESIGN.md
index 6aa0b58..5ac5717 100644
--- a/docs/UI_DESIGN.md
+++ b/docs/UI_DESIGN.md
@@ -50,7 +50,7 @@ Layout sketch (subject to refinement; 4-5 columns):
          BASE
 ```
 
-BASE is prominent because it is the distinctive "programmer display" feature.
+The BASE action (cycle display format) is available via the `Tab` key (documented in the hint row). There is no on-screen BASE button in the keypad grid. This keeps the button layout regular and avoids awkward single-button rows, while still making the feature easily discoverable via the persistent hint.
 
 All important actions have direct keys (digits, operators, =/Enter, Backspace, Tab for BASE, c/C, etc.). The on-screen buttons are primarily visual + mouse targets.
 
diff --git a/internal/ui/ui.go b/internal/ui/ui.go
index b6b75c1..bfb4d27 100644
--- a/internal/ui/ui.go
+++ b/internal/ui/ui.go
@@ -80,8 +80,9 @@ func (a *App) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return a, tick(600*time.Millisecond, "cerr")
 			}
 			a.flash = "base"
-			a.pressedKey = "BASE"
-			return a, tick(140*time.Millisecond, "key")
+			// BASE is Tab-only now (no visual button in the grid).
+			// The "base" flash will highlight the base label in the display row.
+			return a, tick(140*time.Millisecond, "base")
 
 		case "c", "C":
 			a.engine.ClearEntry()
@@ -224,7 +225,6 @@ func (a *App) View() string {
 	opKey := keyStyle.Copy().Foreground(lipgloss.Color("63")).Background(lipgloss.Color("235"))
 	clearKey := keyStyle.Copy().Foreground(lipgloss.Color("203")).Background(lipgloss.Color("52"))
 	modKey := keyStyle.Copy().Foreground(lipgloss.Color("214")) // orange-ish for MOD
-	baseKey := keyStyle.Copy().BorderForeground(lipgloss.Color("63")).Bold(true)
 
 	makeKey := func(label string) string {
 		var st lipgloss.Style
@@ -235,8 +235,6 @@ func (a *App) View() string {
 			st = clearKey
 		case "MOD":
 			st = modKey
-		case "BASE":
-			st = baseKey
 		case "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", ".":
 			st = numKey
 		case "+/-":
@@ -256,23 +254,11 @@ func (a *App) View() string {
 	row3 := lipgloss.JoinHorizontal(lipgloss.Top, makeKey("1"), spacer, makeKey("2"), spacer, makeKey("3"), spacer, makeKey("-"), spacer, makeKey("AC"))
 	row4 := lipgloss.JoinHorizontal(lipgloss.Top, makeKey("0"), spacer, makeKey("."), spacer, makeKey("+/-"), spacer, makeKey("+"), spacer, makeKey("="))
 
-	// Make the BASE row the same width as the other rows.
-	// This ensures the BASE button is nicely centered on its own row
-	// when the whole grid is centered under the display.
-	fullRowWidth := lipgloss.Width(row1)
-	baseOnly := makeKey("BASE")
-	baseRow := lipgloss.NewStyle().
-		Width(fullRowWidth).
-		Align(lipgloss.Center).
-		Render(baseOnly)
-
-	// Compact grid of keys — every row has identical width so the BASE
-	// button sits nicely centered on its row.
-	rawGrid := lipgloss.JoinVertical(lipgloss.Left, row1, row2, row3, row4, baseRow)
+	// Compact 4-row keypad grid (BASE action is Tab-only; see hint).
+	rawGrid := lipgloss.JoinVertical(lipgloss.Left, row1, row2, row3, row4)
 
 	// Center the key grid directly under the display.
-	// No enclosing container or background panel — just the individually
-	// styled keys (each with their own border + color).
+	// No enclosing container — just the individually styled keys.
 	keypad := lipgloss.NewStyle().
 		Width(dispW).
 		Align(lipgloss.Center).