What is the purpose of the walls in "Clash of Clans"?

The purpose of the walls in "Clash of Clans" is to defend the village against enemy attack. Players can encircle their villages with walls to hinder the enemy's advance into the village. There are 11 levels of walls.

Enemies automatically slip through gaps in walls. As such, players can deliberately leave gaps where their defenses are the strongest to deal large amounts of splash damage to larger groups of enemies. Defensive units such as the mortars and wizard towers deal damage to multiple enemies at once.

Flying units can fly over walls. Similarly, archers and wizards can send projectiles over walls and attack the troops and buildings behind them.