diff --git a/src-ui/res/rules.en.yaml b/src-ui/res/rules.en.yaml
index 2d251c305..bdabe2eb1 100644
--- a/src-ui/res/rules.en.yaml
+++ b/src-ui/res/rules.en.yaml
@@ -315,3 +315,4 @@ batten: "Shade some cells on the board.\n1. The numbers outside the grid indicat
 fakearrow: "Draw lines through orthogonally adjacent cells to form a directional loop.\n1. The loop cannot branch off or cross itself.\n2. Exactly one arrow in each outlined region must be shaded.\n3. Two shaded arrows cannot be orthogonally adjacent.\n4. The loop must visit all unshaded arrows and travel in the indicated direction, without turning inside the cell.\n5. Shaded arrows cannot follow the above rule. They must be skipped by the loop, or contain a turn, or go straight in a different direction."
 regional-poly: "Place every shape from the bank into the grid. Shapes can be rotated or mirrored.\n1. All shapes must be used exactly once. There cannot be shapes in the grid that aren't present in the bank.\n2. Two shapes cannot be orthogonally or diagonally adjacent.\n3. Cells marked with a cross cannot be used by a shape.\n4. Every outlined region contains no more than one shape. Shapes cannot overlap region borders."
 twinarea: "Place one number in a cell of each region on the board.\n1. The number in the region should be equal to the size of the region.\n2. Numbers cannot be orthogonally adjacent.\n3. Orthogonally connected gray cells form areas. The sum of the numbers in each area must be equal to the size of the area."
+smullyan: "Shade some cells on the board.\n1. Shaded cells cannot be horizontally or vertically adjacent.\n2. The cells around a number, including the number itself, is called a domain. Unshaded numbers show the amount of shaded cells in its domain.\n3. Shaded numbers must not show the amount of shaded cells in its domain.\n4. All unshaded cells on the board form an orthogonally connected area."