diff --git a/layout.go b/layout.go
index 65c7b47..9d0dcd9 100644
--- a/layout.go
+++ b/layout.go
@@ -14,7 +14,10 @@ import (
 	"github.com/peco/peco/line"
 )
 
-var extraOffset int = 0
+// extraOffset is a platform-specific constant that adds extra vertical
+// space to layout anchors. On Windows, terminals need an additional line
+// reserved at the bottom. Set per-platform via layout_windows.go and
+// layout_notwindows.go.
 
 // ansiLiner is an optional interface for lines that carry ANSI color attributes.
 type ansiLiner interface {
diff --git a/layout_any.go b/layout_any.go
new file mode 100644
index 0000000..521d648
--- /dev/null
+++ b/layout_any.go
@@ -0,0 +1,5 @@
+//go:build !windows
+
+package peco
+
+const extraOffset = 0
diff --git a/layout_windows.go b/layout_windows.go
index 364a61d..36fcf1e 100644
--- a/layout_windows.go
+++ b/layout_windows.go
@@ -1,7 +1,5 @@
 package peco
 
-func init() {
-	// This is the value we pass to anchor offset when we're running
-	// on windows platform
-	extraOffset = 1
-}
+// extraOffset reserves one additional line at the bottom on Windows
+// to account for platform-specific terminal rendering behavior.
+const extraOffset = 1