diff --git a/internal/graphics/vertices.go b/internal/graphics/vertices.go
index dadc8d0df..62ac2c97e 100644
--- a/internal/graphics/vertices.go
+++ b/internal/graphics/vertices.go
@@ -90,7 +90,8 @@ func quadVerticesImpl(sw, sh, x, y, u0, v0, u1, v1, a, b, c, d, tx, ty, cr, cg,
 	// Specifying a range explicitly here is redundant but this helps optimization
 	// to eliminate boundary checks.
 	//
-	// 4*VertexFloatNum is better than 48, but in GopherJS, optimization might not work.
+	// 4*VertexFloatNum is better than 48 in terms of code maintenanceability, but in GopherJS, optimization
+	// might not work.
 	vs := theVerticesBackend.slice(4)[0:48]
 
 	ax, by, cx, dy := a*x, b*y, c*x, d*y
diff --git a/internal/shareable/shareable.go b/internal/shareable/shareable.go
index f9cd825c0..378cc1d04 100644
--- a/internal/shareable/shareable.go
+++ b/internal/shareable/shareable.go
@@ -185,6 +185,10 @@ func (i *Image) Size() (width, height int) {
 	return i.width, i.height
 }
 
+// QuadVertices returns the vertices for rendering a quad.
+//
+// QuadVertices is highly optimized for rendering quads, and that's the most significant difference from
+// PutVertices.
 func (i *Image) QuadVertices(sx0, sy0, sx1, sy1 int, a, b, c, d, tx, ty float32, cr, cg, cb, ca float32) []float32 {
 	if i.backend == nil {
 		i.allocate(true)
@@ -193,6 +197,7 @@ func (i *Image) QuadVertices(sx0, sy0, sx1, sy1 int, a, b, c, d, tx, ty float32,
 	return i.backend.restorable.QuadVertices(sx0+ox, sy0+oy, sx1+ox, sy1+oy, a, b, c, d, tx, ty, cr, cg, cb, ca)
 }
 
+// PutVertices puts the given dest with vertices that can be passed to DrawImage.
 func (i *Image) PutVertex(dest []float32, dx, dy, sx, sy float32, bx0, by0, bx1, by1 float32, cr, cg, cb, ca float32) {
 	if i.backend == nil {
 		i.allocate(true)