diff --git a/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/App.kt b/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/App.kt
index 35df9fd..6a75278 100644
--- a/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/App.kt
+++ b/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/App.kt
@@ -2,34 +2,16 @@ package ch.dissem.yaep.ui.common
 
 import androidx.compose.foundation.Image
 import androidx.compose.foundation.clickable
-import androidx.compose.foundation.layout.Column
-import androidx.compose.foundation.layout.Row
-import androidx.compose.foundation.layout.aspectRatio
-import androidx.compose.foundation.layout.fillMaxHeight
-import androidx.compose.foundation.layout.fillMaxWidth
-import androidx.compose.foundation.layout.padding
-import androidx.compose.foundation.layout.wrapContentHeight
+import androidx.compose.foundation.layout.*
 import androidx.compose.foundation.lazy.grid.GridCells
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.material3.HorizontalDivider
 import androidx.compose.material3.OutlinedCard
-import androidx.compose.runtime.Composable
-import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
-import androidx.compose.runtime.remember
-import androidx.compose.runtime.setValue
+import androidx.compose.runtime.*
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.unit.dp
-import ch.dissem.yaep.domain.Clue
-import ch.dissem.yaep.domain.Grid
-import ch.dissem.yaep.domain.HorizontalClue
-import ch.dissem.yaep.domain.ItemClass
-import ch.dissem.yaep.domain.NeighbourClue
-import ch.dissem.yaep.domain.OrderClue
-import ch.dissem.yaep.domain.SameColumnClue
-import ch.dissem.yaep.domain.TripletClue
-import ch.dissem.yaep.domain.generateGame
+import ch.dissem.yaep.domain.*
 import org.jetbrains.compose.resources.painterResource
 import yaep.commonui.generated.resources.Res
 import yaep.commonui.generated.resources.neighbour
@@ -66,15 +48,30 @@ fun PuzzleGrid(
                     .fillMaxWidth()
                     .wrapContentHeight()
             ) {
+                val allOptions = row.options
                 for (item in row) {
+                    var selection by remember { mutableStateOf(item.selection) }
+                    val options = remember { allOptions.map { Toggleable(it, item.options.contains(it)) } }
+                    LaunchedEffect(item) {
+                        item.removedListeners.add { removed ->
+                            options
+                                .filter { removed.contains(it.item) }
+                                .forEach { it.enabled = false }
+                        }
+                        item.selectionChangedListeners.add {
+                            selection = it
+                        }
+                    }
                     Selector(
                         modifier = Modifier
                             .padding(8.dp)
                             .weight(1f),
-                        category = row.category,
-                        options = item.options,
-                        selectedItem = item.selection,
-                        onSelectItem = { item.selection = it }
+                        options = options,
+                        selectedItem = selection,
+                        onSelectItem = {
+                            item.selection = it
+                            grid.cleanupOptions()
+                        }
                     )
                 }
             }
@@ -169,4 +166,4 @@ fun VerticalClue(modifier: Modifier = Modifier, clue: SameColumnClue<*, *>) {
             DrawItem(modifier = Modifier.weight(1f), clue.b)
         }
     }
-}
\ No newline at end of file
+}
diff --git a/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/selector.kt b/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/selector.kt
index 3b48880..9e0de46 100644
--- a/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/selector.kt
+++ b/commonUI/src/main/kotlin/ch/dissem/yaep/ui/common/selector.kt
@@ -1,7 +1,6 @@
 package ch.dissem.yaep.ui.common
 
-import androidx.compose.foundation.Canvas
-import androidx.compose.foundation.clickable
+import androidx.compose.foundation.*
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.aspectRatio
 import androidx.compose.foundation.layout.fillMaxSize
@@ -9,24 +8,28 @@ import androidx.compose.foundation.lazy.grid.GridCells
 import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.material3.OutlinedCard
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.input.pointer.PointerButton
 import androidx.compose.ui.text.TextStyle
 import androidx.compose.ui.text.drawText
 import androidx.compose.ui.text.rememberTextMeasurer
 import ch.dissem.yaep.domain.Item
 import ch.dissem.yaep.domain.ItemClass
-import ch.dissem.yaep.domain.ItemClassCompanion
 import ch.dissem.yaep.ui.common.theme.emojiFontFamily
 import kotlin.math.min
 
+@OptIn(ExperimentalFoundationApi::class)
 @Composable
 fun <C : ItemClass<C>> Selector(
     modifier: Modifier = Modifier,
-    category: ItemClassCompanion<C>,
-    options: List<Item<C>>,
+    options: List<Toggleable<Item<C>>>,
     selectedItem: Item<C>?,
-    onSelectItem: (Item<C>?) -> Unit
+    onSelectItem: (Item<C>?) -> Unit,
 ) {
     if (selectedItem != null) {
         DrawItem(item = selectedItem, modifier = modifier.clickable { onSelectItem(null) })
@@ -40,8 +43,19 @@ fun <C : ItemClass<C>> Selector(
                 for (option in options) {
                     item {
                         DrawItem(
-                            item = option,
-                            modifier = Modifier.clickable { onSelectItem(option) }
+                            item = option.item,
+                            modifier = Modifier
+                                .alpha(if (option.enabled) 1f else 0.1f)
+                                .combinedClickable(
+                                    onClick = { onSelectItem(option.item) },
+                                    onLongClick = { option.enabled = false }
+                                )
+                                .onClick(
+                                    matcher = PointerMatcher.mouse(PointerButton.Secondary),
+                                    onClick = {
+                                        option.enabled = false
+                                    }
+                                )
                         )
                     }
                 }
@@ -81,7 +95,10 @@ fun <C : ItemClass<C>> DrawItem(
                 drawText(
                     textMeasurer = textMeasurer,
                     text = emoji,
-                    style = TextStyle(fontSize = fontSize, fontFamily = emojiFontFamily ?: TextStyle.Default.fontFamily),
+                    style = TextStyle(
+                        fontSize = fontSize,
+                        fontFamily = emojiFontFamily ?: TextStyle.Default.fontFamily
+                    ),
                     topLeft = offset
                 )
             }
@@ -89,3 +106,23 @@ fun <C : ItemClass<C>> DrawItem(
     }
 }
 
+class Toggleable<T>(val item: T, enabled: Boolean = true) {
+
+    var enabled: Boolean by mutableStateOf(enabled)
+
+    override fun equals(other: Any?): Boolean {
+        if (this === other) return true
+        if (other !is Toggleable<*>) return false
+
+        if (item != other.item) return false
+        if (enabled != other.enabled) return false
+
+        return true
+    }
+
+    override fun hashCode(): Int {
+        var result = item.hashCode()
+        result = 31 * result + enabled.hashCode()
+        return result
+    }
+}
diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/GameCell.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/GameCell.kt
index a5b2b14..76100c3 100644
--- a/domain/src/main/kotlin/ch/dissem/yaep/domain/GameCell.kt
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/GameCell.kt
@@ -1,10 +1,20 @@
 package ch.dissem.yaep.domain
 
 class GameCell<C : ItemClass<C>>(
-    var selection: Item<C>?,
+    selection: Item<C>?,
     val solution: Item<C>,
-    val options: MutableList<Item<C>>
-)
+    options: Collection<Item<C>>
+) {
+    val selectionChangedListeners = mutableListOf<(Item<C>?) -> Unit>()
+    val removedListeners = mutableListOf<(Collection<Item<C>>) -> Unit>()
+
+    var selection: Item<C>? = selection
+        set(value) {
+            field = value
+            selectionChangedListeners.forEach { listener -> listener(value) }
+        }
+    val options = ObservableSet(options.toMutableSet()) { removedListeners.forEach { listener -> listener(it) } }
+}
 
 fun <C : ItemClass<C>> GameCell<C>?.mayBe(item: Item<C>, mayHaveSelection: Boolean = true) =
     this != null &&
@@ -14,3 +24,4 @@ fun <C : ItemClass<C>> GameCell<C>?.isA(item: Item<C>) =
     this != null && selection == item
 
 fun <C : ItemClass<C>> GameCell<C>?.hasNoSelection() = this != null && this.selection == null
+
diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/GameRow.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/GameRow.kt
index 32d8808..1bf65b6 100644
--- a/domain/src/main/kotlin/ch/dissem/yaep/domain/GameRow.kt
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/GameRow.kt
@@ -7,8 +7,18 @@ class GameRow<C : ItemClass<C>>(
 ) : List<GameCell<C>> by cells {
     fun indexOf(element: C) = indexOfFirst { it.selection?.itemType == element }
 
-    fun updateOptions() {
-        val selections = mapNotNull { it.selection }
-        forEach { it.options.removeAll(selections) }
+    fun cleanupOptions() {
+        cells.forEach { cleanupOptions(it) }
     }
+
+    private fun cleanupOptions(cell: GameCell<C>) {
+        if (cell.options.size == 1 && cell.selection == null) {
+            cell.selection = cell.options.first()
+            filter { otherCell -> otherCell != cell && otherCell.selection == null }.forEach { otherCell ->
+                otherCell.options.remove(cell.selection)
+                cleanupOptions(otherCell)
+            }
+        }
+    }
+
 }
diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/Grid.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/Grid.kt
index c59287c..eaa7f9a 100644
--- a/domain/src/main/kotlin/ch/dissem/yaep/domain/Grid.kt
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/Grid.kt
@@ -6,7 +6,7 @@ class Grid(
 ) : List<GameRow<ItemClass<*>>> by rows as List<GameRow<ItemClass<*>>> {
 
     val cells: List<GameCell<*>>
-        get() = rows.flatten() as List<GameCell<*>>
+        get() = rows.flatten()
 
     fun <C : ItemClass<C>> indexOf(element: C): Int {
         return this[element.companion]
@@ -27,6 +27,10 @@ class Grid(
             row.joinToString("") { it.selection?.symbol ?: "  " }
         }
     }
+
+    fun cleanupOptions() {
+        forEach { row -> row.cleanupOptions() }
+    }
 }
 
 fun List<List<Item<ItemClass<*>>>>.toGrid() = Grid(
diff --git a/domain/src/main/kotlin/ch/dissem/yaep/domain/ObservableSet.kt b/domain/src/main/kotlin/ch/dissem/yaep/domain/ObservableSet.kt
new file mode 100644
index 0000000..101f11e
--- /dev/null
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/ObservableSet.kt
@@ -0,0 +1,29 @@
+package ch.dissem.yaep.domain
+
+class ObservableSet<E> private constructor(
+    private val mutableSet: MutableSet<E>,
+    private val onElementRemoved: (Set<E>) -> Unit
+) : MutableSet<E> by mutableSet {
+    constructor(elements: Collection<E>, onElementRemoved: (Set<E>) -> Unit) : this(
+        elements.toMutableSet(),
+        onElementRemoved
+    )
+
+    override fun remove(element: E): Boolean {
+        return observeRemoval(setOf(element)) { mutableSet.remove(element) }
+    }
+
+    override fun removeAll(elements: Collection<E>): Boolean =
+        observeRemoval(elements.toSet(), mutableSet::removeAll)
+
+    override fun retainAll(elements: Collection<E>): Boolean =
+        observeRemoval(elements.toSet(), mutableSet::retainAll)
+
+    private fun observeRemoval(values: Set<E>, operation: (Set<E>) -> Boolean): Boolean {
+        val removed = operation(values)
+        if (removed) {
+            onElementRemoved(values)
+        }
+        return removed
+    }
+}
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 d4c0822..09b2dca 100644
--- a/domain/src/main/kotlin/ch/dissem/yaep/domain/generator.kt
+++ b/domain/src/main/kotlin/ch/dissem/yaep/domain/generator.kt
@@ -74,7 +74,7 @@ internal fun solve(
 //                        .forEach { it.options.removeAll(groupOptions) }
 //                }
 //        }
-        grid.forEach { row -> row.forEach { cell -> row.cleanupOptions(cell) } }
+        grid.cleanupOptions()
     } while (removedOptions)
 
     // If any cell has no items left, the puzzle has no solution.
@@ -92,16 +92,6 @@ internal enum class PuzzleSolution {
     MULTIPLE_SOLUTIONS
 }
 
-fun <C : ItemClass<C>> GameRow<C>.cleanupOptions(cell: GameCell<C>) {
-    if (cell.options.size == 1 && cell.selection == null) {
-        cell.selection = cell.options.first()
-        filter { otherCell -> otherCell != cell && otherCell.selection == null }.forEach { otherCell ->
-            otherCell.options.remove(cell.selection)
-            cleanupOptions(otherCell)
-        }
-    }
-}
-
 fun getAllClues(rows: List<List<Item<ItemClass<*>>>>): MutableSet<Clue> {
     val clues = mutableSetOf<Clue>()
     rows.forEach { row ->