diff --git a/common/renderer.go b/common/renderer.go
index 89410c4..ad83823 100644
--- a/common/renderer.go
+++ b/common/renderer.go
@@ -275,17 +275,17 @@ func (r *Renderer) RenderBlock(block *Block, colors *Colors) (err error) {
 	return
 }
 
-func (a Area) Contains(x, z int16) bool {
+func (a Area) contains(x, z int16) bool {
 	return x >= a.X1 && x <= a.X2 && z >= a.Z1 && z <= a.Z2
 }
 
-func (a Area) IsHigher() bool {
+func (a Area) higher() bool {
 	return a.Z2-a.Z1 > a.X2-a.X1
 }
 
 func areasContain(areas []Area, x, z int16) bool {
 	for _, r := range areas {
-		if r.Contains(x, z) {
+		if r.contains(x, z) {
 			return true
 		}
 	}
@@ -317,7 +317,7 @@ func (r *Renderer) UncoveredAreas(newAreas, oldAreas []Area) []Area {
 					var xFirst bool
 					// Try to extend in the direction with most gain
 					// of blocks.
-					if area.IsHigher() { // Higher means to win more blocks in x direction.
+					if area.higher() { // Higher means to win more blocks in x direction.
 						xFirst = true
 					}
 				dirs: