diff --git a/rollup.config.js b/rollup.config.js
index b3fc336..64c326a 100644
--- a/rollup.config.js
+++ b/rollup.config.js
@@ -44,7 +44,7 @@ export default {
 			compilerOptions: {
 				// enable run-time checks when not in production
 				dev: !production
-			}
+			},
 		}),
 		// we'll extract any component CSS out into
 		// a separate file - better for performance
diff --git a/src/FilterItem.svelte b/src/FilterItem.svelte
index dcc53a9..b603df8 100644
--- a/src/FilterItem.svelte
+++ b/src/FilterItem.svelte
@@ -1,74 +1,80 @@
 <script>
   import { writable } from 'svelte/store';
-  import { tick } from 'svelte';
+  import { tick, createEventDispatcher } from 'svelte';
 
   import TriStateCheckbox from './TriStateCheckbox.svelte';
-  import { createTriState, UNCHECKED, CHECKED, WEIRD } from './stores';
+  import { createTriState, createTriStates, UNCHECKED, CHECKED, WEIRD } from './stores';
 
   export let item = null;
 
   export let children = [];
   export let selected = [];
   export let filtering = createTriState(CHECKED);
-  let subfiltering = Array(Object.keys(children).length).fill(createTriState(CHECKED));
+  let subfiltering = createTriStates(CHECKED, Object.entries(children).length);
 
-  
   function isVal(val) {
     return function (other) {
       return other === val;
     }
   }
 
- 
-  subfiltering.forEach((subfilter, j) => {
-    subfilter.subscribe(subvalue => {
-      console.log('subfiltering', Object.entries(children)[j][0], 'newValue=', subvalue, 'prevValue=', subfiltering[j], '$filtering=', $filtering);
-      const others = subfiltering.filter((_, i) => i !== j);
-      const areAllOthers = others.every(isVal(CHECKED));
-      const isThereAny = !others.some(isVal(UNCHECKED));
+  function areAllChecked(values) {
+    return values.every(isVal(CHECKED));
+  }
 
-      tick().then(() => {
-        if (subvalue === CHECKED && areAllOthers && $filtering !== CHECKED) {
-          console.log('check $filtering');
-          filtering.setChecked();
-        } else if (subvalue === UNCHECKED && isThereAny && $filtering !== UNCHECKED) {
-          console.log('uncheck $filtering');
-          filtering.setUnchecked();
-        } else if (!areAllOthers && !isThereAny && $filtering !== WEIRD) {
-          console.log(Object.entries(children)[j][0], 'partial checking');
-          filtering.setWeird();
-        }
-      });
-    });
-  });
+  function areAllUnchecked(values) {
+    return values.every(isVal(UNCHECKED));
+  }
 
+  function handleChildChange(i) {
+    return function handler(evt) {
+      subfiltering.setAt(i, evt.detail.value);
+    }
+  }
 
-  filtering.subscribe(value => {
-    console.log('filtering', item, 'newValue=', value, 'prevValue=', $filtering);
-    if (value !== $filtering) {
-      switch (value) {
-        case CHECKED:
-          subfiltering.forEach(subfilter => subfilter.setChecked());
-          break;
-        case UNCHECKED:
-          subfiltering.forEach(subfilter => subfilter.setUnchecked());
-          break;
-      }
+  subfiltering.subscribe(subvalues => {
+    console.log('new subvalues', subvalues);
+    if (areAllChecked(subvalues) && $filtering !== CHECKED) {
+      filtering.setChecked();
+    } else if (areAllUnchecked(subvalues) && $filtering !== UNCHECKED) {
+      filtering.setUnchecked();
+    } else if (!areAllChecked(subvalues) && !areAllUnchecked(subvalues) && $filtering !== WEIRD) {
+      filtering.setWeird();
     }
   });
 
+  if (subfiltering.length > 0) {
+    filtering.subscribe(value => {
+      console.log(item, value);
+      switch (value) {
+        case CHECKED:
+          subfiltering.updateAll(_ => CHECKED);
+          break;
+        case UNCHECKED:
+          subfiltering.updateAll(_ => UNCHECKED);
+          break;
+      }
+    });
+  }
+
+  const dispatch = createEventDispatcher();
+  function handleChange(evt) {
+    filtering.set(evt.detail.value);
+    dispatch('change', { value: evt.detail.value });
+  }
+
 </script>
 
 {#if item != null}
 <li>
-<TriStateCheckbox bind:state={filtering} value={item} initialValue={true} />
+<TriStateCheckbox state={$filtering} on:change={handleChange} value={item} initialValue={true} />
 <span>{item}</span>
   <ul>
   {#each Object.entries(children) as [toplevel, subchildren], i}
     {#if subchildren}
-      <svelte:self item={toplevel} children={subchildren} bind:filtering={subfiltering[i]} />
+      <svelte:self item={toplevel} children={subchildren} on:change={handleChildChange(i)} filtering={subfiltering.storeAt(i)} />
     {:else}
-      <svelte:self item={toplevel} bind:filtering={subfiltering[i]} />
+      <svelte:self item={toplevel} on:change={handleChildChange(i)} filtering={subfiltering.storeAt(i)} />
     {/if}
   {/each}
   </ul>
diff --git a/src/TriStateCheckbox.svelte b/src/TriStateCheckbox.svelte
index b47bd7f..002d29a 100644
--- a/src/TriStateCheckbox.svelte
+++ b/src/TriStateCheckbox.svelte
@@ -3,31 +3,35 @@
   export let state;
   export let value;
 
-  import { createTriState, UNCHECKED, CHECKED, WEIRD } from './stores';
+  import { UNCHECKED, CHECKED, WEIRD } from './stores';
+  import { createEventDispatcher } from 'svelte';
+
+  const dispatch = createEventDispatcher();
    
   let node;
+  let checkedValue = false;
 
-  state.subscribe(val => {
-    if (!node) return;
+  $: {
+    if (node) {
+      if (state === CHECKED) {
+        checkedValue = true;
+      } else if (state === UNCHECKED) {
+        checkedValue = false;
+      }
 
-    if (val === CHECKED) {
-      checkedValue = true;
-    } else if (val === UNCHECKED) {
-      checkedValue = false;
-    }
+      node.indeterminate = state === WEIRD;
 
-    node.indeterminate = val === WEIRD;
-  });
-
-  function handleClick(evt) {
-    if (evt.target.checked) {
-      state.setChecked();
-    } else if (!evt.target.checked) {
-      state.setUnchecked();
     }
   }
 
-  let checkedValue = false;
+  function handleClick(evt) {
+    if (evt.target.checked) {
+      state = CHECKED;
+    } else if (!evt.target.checked) {
+      state = UNCHECKED;
+    }
+    dispatch('change', { value: state });
+  }
 </script>
 
 <input type="checkbox" checked={checkedValue} on:click={handleClick} bind:this={node} value={value} />
diff --git a/src/stores.js b/src/stores.js
index 43ba7fa..05db473 100644
--- a/src/stores.js
+++ b/src/stores.js
@@ -16,3 +16,31 @@ export function createTriState(initialValue) {
   }
 }
 
+export function createTriStates(initialValue, length) {
+  const { subscribe, update, set } = writable(Array.from({length}, e => initialValue));
+
+  const setAt = (index, newValue) => {
+      update(array => [...array.slice(0, index), newValue, ...array.slice(index + 1)]);
+  };
+
+  return {
+    subscribe,
+    set,
+    setAt,
+    length,
+    storeAt: index => {
+      const set = value => setAt(index, value);
+      return {
+        subscribe: fun => subscribe(subvalues => fun(subvalues[index])),
+        set,
+        setUnchecked: () => set(UNCHECKED),
+        setWeird: () => set(WEIRD),
+        setChecked: () => set(CHECKED)
+      };
+    },
+    updateAll: fun => {
+      update(array => array.map(fun));
+    }
+  }
+}
+