Why the access tunnels to igloos often curve downwards?

The access tunnels to igloos often curve downwards in order to help trap heat inside the igloo and keep it warmer than the outside air. The design of the tunnel also helps to keep the igloo more structurally sound by preventing snow from collapsing onto the entrance. The curved shape of the tunnel also prevents the wind from blowing directly into the igloo, further helping to maintain a warm and comfortable temperature inside the igloo. Additionally, this design helps to keep the entrance of the igloo away from the elements and provides extra protection from the elements. Finally, the curved shape of the tunnel helps to keep out drafts, which can cause the temperature inside the igloo to drop.