diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/UnsolvablePuzzleException.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/UnsolvablePuzzleException.kt
new file mode 100644
index 0000000..a176365
--- /dev/null
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/UnsolvablePuzzleException.kt
@@ -0,0 +1,3 @@
+package ch.dissem.yaep.domain
+
+class UnsolvablePuzzleException(e: Exception) : Exception(e)
diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/clues.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/clues.kt
index 5b7ce01..1f62b6b 100644
--- a/domain/src/main/kotlin/ch/dissem/yaep/domain/clues.kt
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/clues.kt
@@ -2,6 +2,11 @@ package ch.dissem.yaep.domain
 
 sealed class Clue {
     abstract fun isRuleViolated(grid: Grid): Boolean
+
+    /**
+     * @return `true` if any option was removed
+     */
+    abstract fun removeForbiddenOptions(grid: Grid): Boolean
 }
 
 sealed class HorizontalClue : Clue()
@@ -42,6 +47,37 @@ class NeighbourClue<A : ItemClass<A>, B : ItemClass<B>>(val a: Item<A>, val b: I
         return true
     }
 
+    override fun removeForbiddenOptions(grid: Grid): Boolean {
+        val rowA: GameRow<A> = grid[aType.companion]
+        val rowB: GameRow<B> = grid[bType.companion]
+
+        var removed = removeForbiddenOptions(a, b, rowA, rowB)
+        removed = removeForbiddenOptions(b, a, rowB, rowA) || removed
+
+        return removed
+    }
+
+    private fun <X : ItemClass<X>, Y : ItemClass<Y>> removeForbiddenOptions(
+        x: Item<X>,
+        y: Item<Y>,
+        rowX: GameRow<X>,
+        rowY: GameRow<Y>
+    ): Boolean {
+        var removed = false
+
+        for (iX in rowX.indices) {
+            val cellX = rowX[iX]
+            if (cellX.options.contains(x)) {
+                if (!rowY.getOrNull(iX - 1).mayBe(y) && !rowY.getOrNull(iX + 1).mayBe(y)) {
+                    cellX.options.remove(x)
+                    removed = true
+                }
+            }
+        }
+
+        return removed
+    }
+
     override fun toString() = "$aType is next to $bType"
 }
 
@@ -69,6 +105,24 @@ class OrderClue<L : ItemClass<L>, R : ItemClass<R>>(val left: Item<L>, val right
         return rowLeft.indexOfFirst { it.mayBe(left) } >= rowRight.indexOfLast { it.mayBe(right) }
     }
 
+    override fun removeForbiddenOptions(grid: Grid): Boolean {
+        val rowL = grid[leftType.companion]
+        val rowR = grid[rightType.companion]
+
+        val firstL = rowL.indexOfFirst { it.options.contains(left) }
+        val lastR = rowR.indexOfLast { it.options.contains(right) }
+
+        var removed = false
+        try {
+            rowL.takeLast(rowL.size - lastR + 1)
+                .forEach { removed = it.options.remove(left) || removed }
+            rowR.take(firstL).forEach { removed = it.options.remove(right) || removed }
+        } catch (e: IllegalArgumentException) {
+            throw UnsolvablePuzzleException(e)
+        }
+        return removed
+    }
+
     override fun toString() = "$leftType is left of $rightType"
 }
 
@@ -161,6 +215,10 @@ class TripletClue<A : ItemClass<A>, B : ItemClass<B>, C : ItemClass<C>>(
         return true
     }
 
+    override fun removeForbiddenOptions(grid: Grid): Boolean {
+        TODO("Not yet implemented")
+    }
+
     override fun toString(): String =
         "$bType is between the neighbours $aType and $cType to both sides"
 }
@@ -196,6 +254,25 @@ class SameColumnClue<A : ItemClass<A>, B : ItemClass<B>>(val a: Item<A>, val b:
         return true
     }
 
+    override fun removeForbiddenOptions(grid: Grid): Boolean {
+        val rowA = grid[aType.companion]
+        val rowB = grid[bType.companion]
+
+        var removed = false
+        for (i in rowA.indices) {
+            val cellA = rowA[i]
+            val cellB = rowB[i]
+
+            if (!cellA.mayBe(a)) {
+                removed = cellB.options.remove(b) || removed
+            }
+            if (!cellB.mayBe(b)) {
+                removed = cellA.options.remove(a) || removed
+            }
+        }
+        return removed
+    }
+
     override fun toString(): String = "$aType and $bType are in the same column"
 }
 
@@ -209,5 +286,18 @@ class PositionClue<C : ItemClass<C>>(val item: Item<C>, val index: Int) : Clue()
         return grid[item].mayBe(item)
     }
 
+    override fun removeForbiddenOptions(grid: Grid): Boolean {
+        val row = grid[itemType.companion]
+        var removed = false
+        row.forEachIndexed { i, cell ->
+            if (i == index) {
+                removed = cell.options.retainAll { it == item } || removed
+            } else {
+                removed = cell.options.remove(item) || removed
+            }
+        }
+        return removed
+    }
+
     override fun toString() = "$itemType is at position $index"
 }
diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/generator.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/generator.kt
index e690791..5f7ba53 100644
--- a/domain/src/main/kotlin/ch/dissem/yaep/domain/generator.kt
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/generator.kt
@@ -44,23 +44,29 @@ internal fun solve(
     // Start with a grid where each cell is a list of all possible items.
 
     // First, set the positions of the items that are already known.
-    clues.filterIsInstance<PositionClue<ItemClass<*>>>().forEach { position ->
-        val row = grid[position.itemType.companion]
-        val cell = row[position.index]
-        cell.options.retainAll { it == position.item }
-        row.cleanupOptions(cell)
-    }
+//    clues.filterIsInstance<PositionClue<ItemClass<*>>>().forEach { position ->
+//        position.removeForbiddenOptions(grid)
+//    }
+//    grid.forEach { row -> row.forEach { cell -> row.cleanupOptions(cell) } }
 
     // For each clue, remove any items that violate the clue.
     // If any cell has only one item left, remove that item from all other cells.
     // Repeat until no more items can be removed.
-    val otherClues = clues.filter { it !is PositionClue<*> }
+//    val otherClues = clues.filter { it !is PositionClue<*> }
     var removedOptions: Boolean
     do {
         removedOptions = false
-        grid.forEach { row ->
-            removedOptions = row.tryOptionsForClues(grid, otherClues) || removedOptions
+        try {
+            clues.forEach { clue ->
+                removedOptions = clue.removeForbiddenOptions(grid) || removedOptions
+            }
+        } catch (e: UnsolvablePuzzleException) {
+            return NO_SOLUTION
         }
+        grid.forEach { row -> row.forEach { cell -> row.cleanupOptions(cell) } }
+//        grid.forEach { row ->
+//            removedOptions = row.tryOptionsForClues(grid, otherClues) || removedOptions
+//        }
     } while (removedOptions)
 
     // If any cell has no items left, the puzzle has no solution.
@@ -70,15 +76,16 @@ internal fun solve(
     if (grid.cells.all { it.selection != null }) return SOLVABLE
 
     // If there are still cells with multiple items, pick one and try each item in turn, then go back to step 2.
-    return if (
-        grid.cells
-            .filter { it.selection == null }
-            .any { it.countSolutions(grid, clues) == 1 }
-    ) {
-        SOLVABLE
-    } else {
-        MULTIPLE_SOLUTIONS
-    }
+//    return if (
+//        grid.cells
+//            .filter { it.selection == null }
+//            .any { it.countSolutions(grid, clues) == 1 }
+//    ) {
+//        SOLVABLE
+//    } else {
+//        MULTIPLE_SOLUTIONS
+//    }
+    return MULTIPLE_SOLUTIONS
 }
 
 internal fun <C : ItemClass<C>> GameCell<C>.countSolutions(