diff --git a/library/game_progress/DesertProgress.gd b/library/game_progress/DesertProgress.gd
index c860a63..152af14 100644
--- a/library/game_progress/DesertProgress.gd
+++ b/library/game_progress/DesertProgress.gd
@@ -29,7 +29,7 @@ func renew_world(pc_coord: Game_IntCoord) -> void:
 
 
 func end_world(_pc_coord: Game_IntCoord) -> void:
-	var count := _count_worms * Game_DesertData.SANDWORM_CONSUME_TURN
+	var count := int(max(0, _count_worms * 2 - 1))
 
 	# Do not subtract count if game ends.
 	_ref_CountDown.subtract_count(count)
diff --git a/library/npc_data/DesertData.gd b/library/npc_data/DesertData.gd
index b1fa714..0df5dbf 100644
--- a/library/npc_data/DesertData.gd
+++ b/library/npc_data/DesertData.gd
@@ -23,5 +23,4 @@ const WORM_DISTANCE := 5
 const MOVE_STRAIGHT := 60
 
 const RESTORE_TURN := 7
-const SANDWORM_CONSUME_TURN := 2
 const RENDER_RANGE := 8
diff --git a/user/doc/desert.md b/user/doc/desert.md
index 5743a41..d6b4a68 100644
--- a/user/doc/desert.md
+++ b/user/doc/desert.md
@@ -12,9 +12,9 @@ Every turn a sandworm moves one step in a random direction. It has a higher chan
 
 Dunes are composed of sand walls (#) and spices (?). They are created by a living sandworm. The more spices a sandworm has, the more spices will be left behind. You can bump and destroy a wall or bump and collect a spice just as from a sandworm. You do not move when bumping. It can be used as a poor man's waiting key.
 
-You might lose due to one of three reasons.
+You might lose the game due to one of three reasons.
 
-Firstly, you can survive in desert for at most 24 turns. Moving and bumping costs 1 turn. If you start your turn beside a sandworm, every adjacent sandworm segment reduces your remaining time by 2 turns. Bumping a common or quality spice restores 6 turns. You lose if you have not collected 3 spices when your last turn ends.
+Firstly, you can survive in desert for at most 24 turns. Moving and bumping costs 1 turn. Starting your turn beside a sandworm costs an extra `2N - 1` turns, where `N` is the number of adjacent sandworm segments. Bumping a common or quality spice restores 6 turns. You lose if you have not collected 3 spices when your last turn ends.
 
 Secondly, PC's symbol turns into a rectangle when being adjacent to a sandworm's head. The game ends if the sandworm intends to move into PC's position the next turn.