diff --git a/src/app/features/lobby/Lobby.tsx b/src/app/features/lobby/Lobby.tsx
index 7aa20ab3..727fe5e3 100644
--- a/src/app/features/lobby/Lobby.tsx
+++ b/src/app/features/lobby/Lobby.tsx
@@ -36,6 +36,7 @@ import { getSpaceRoomPath } from '../../pages/pathUtils';
 import { HierarchyItemMenu } from './HierarchyItemMenu';
 import { StateEvent } from '../../../types/matrix/room';
 import { AfterItemDropTarget, CanDropCallback, useDnDMonitor } from './DnD';
+import { ASCIILexicalTable, orderKeys } from '../../utils/ASCIILexicalTable';
 
 export function Lobby() {
   const navigate = useNavigate();
@@ -45,6 +46,7 @@ export function Lobby() {
   const allJoinedRooms = useMemo(() => new Set(allRooms), [allRooms]);
   const space = useSpace();
   const spacePowerLevels = usePowerLevels(space);
+  const lex = useMemo(() => new ASCIILexicalTable(' '.charCodeAt(0), '~'.charCodeAt(0), 6), []);
 
   const scrollRef = useRef<HTMLDivElement>(null);
   const heroSectionRef = useRef<HTMLDivElement>(null);
@@ -144,13 +146,118 @@ export function Lobby() {
     [getRoom, space.roomId, roomsPowerLevels, canEditSpaceChild]
   );
 
+  const reorderSpace = useCallback(
+    (item: HierarchyItem, containerItem: HierarchyItem) => {
+      if (!item.parentId) return;
+
+      const childItems = flattenHierarchy
+        .filter((i) => i.parentId && i.space)
+        .filter((i) => i.roomId !== item.roomId);
+
+      const beforeIndex = childItems.findIndex((i) => i.roomId === containerItem.roomId);
+      const insertIndex = beforeIndex + 1;
+
+      childItems.splice(insertIndex, 0, {
+        ...item,
+        content: { ...item.content, order: undefined },
+      });
+
+      const currentOrders = childItems.map((i) => {
+        if (typeof i.content.order === 'string' && lex.has(i.content.order)) {
+          return i.content.order;
+        }
+        return undefined;
+      });
+
+      const newOrders = orderKeys(lex, currentOrders);
+
+      newOrders?.forEach((orderKey, index) => {
+        const itm = childItems[index];
+        if (!itm || !itm.parentId) return;
+        const parentPL = roomsPowerLevels.get(itm.parentId);
+        const canEdit = parentPL && canEditSpaceChild(parentPL);
+        if (canEdit && orderKey !== currentOrders[index]) {
+          mx.sendStateEvent(
+            itm.parentId,
+            StateEvent.SpaceChild,
+            { ...itm.content, order: orderKey },
+            itm.roomId
+          );
+        }
+      });
+    },
+    [mx, flattenHierarchy, lex, roomsPowerLevels, canEditSpaceChild]
+  );
+
+  const reorderRoom = useCallback(
+    (item: HierarchyItem, containerItem: HierarchyItem): void => {
+      if (!item.parentId) {
+        return;
+      }
+      const containerParentId: string = containerItem.space
+        ? containerItem.roomId
+        : containerItem.parentId;
+      const itemContent = item.content;
+
+      if (item.parentId !== containerParentId) {
+        mx.sendStateEvent(item.parentId, StateEvent.SpaceChild, {}, item.roomId);
+      }
+
+      const childItems = flattenHierarchy
+        .filter((i) => i.parentId === containerParentId && !item.space)
+        .filter((i) => i.roomId !== item.roomId);
+
+      const beforeItem: HierarchyItem | undefined = containerItem.space ? undefined : containerItem;
+      const beforeIndex = childItems.findIndex((i) => i.roomId === beforeItem?.roomId);
+      const insertIndex = beforeIndex + 1;
+
+      childItems.splice(insertIndex, 0, {
+        ...item,
+        parentId: containerParentId,
+        content: { ...itemContent, order: undefined },
+      });
+
+      const currentOrders = childItems.map((i) => {
+        if (typeof i.content.order === 'string' && lex.has(i.content.order)) {
+          return i.content.order;
+        }
+        return undefined;
+      });
+
+      const newOrders = orderKeys(lex, currentOrders);
+
+      newOrders?.forEach((orderKey, index) => {
+        const itm = childItems[index];
+        if (itm && orderKey !== currentOrders[index]) {
+          mx.sendStateEvent(
+            containerParentId,
+            StateEvent.SpaceChild,
+            { ...itm.content, order: orderKey },
+            itm.roomId
+          );
+        }
+      });
+    },
+    [mx, flattenHierarchy, lex]
+  );
+
   useDnDMonitor(
     scrollRef,
     setDraggingItem,
-    useCallback((item, container) => {
-      console.log(item, container);
-      // TODO: prompt when dragging restricted room of private space to public space and etc.
-    }, [])
+    useCallback(
+      (item, container) => {
+        if (!canDrop(item, container)) {
+          return;
+        }
+        if (item.space) {
+          reorderSpace(item, container.item);
+        } else {
+          reorderRoom(item, container.item);
+          // TODO: prompt when dragging restricted room of private space to public space and etc.
+        }
+      },
+      [reorderRoom, reorderSpace, canDrop]
+    )
   );
 
   const addSpaceRoom = (roomId: string) => setSpaceRooms({ type: 'PUT', roomId });
diff --git a/src/app/hooks/useSpaceHierarchy.ts b/src/app/hooks/useSpaceHierarchy.ts
index 6a336ad1..b0c52598 100644
--- a/src/app/hooks/useSpaceHierarchy.ts
+++ b/src/app/hooks/useSpaceHierarchy.ts
@@ -6,6 +6,7 @@ import { roomToParentsAtom } from '../state/room/roomToParents';
 import { MSpaceChildContent, StateEvent } from '../../types/matrix/room';
 import { getAllParents, getStateEvents, isValidChild } from '../utils/room';
 import { isRoomId } from '../utils/matrix';
+import { SortFunc } from '../utils/sort';
 
 export type HierarchyItem =
   | {
@@ -22,6 +23,26 @@ export type HierarchyItem =
       space?: false;
       parentId: string;
     };
+
+const hierarchyItemByOrder: SortFunc<HierarchyItem> = (a, b) => {
+  const aOrder = a.content.order;
+  const bOrder = b.content.order;
+  const aTs = a.ts;
+  const bTs = b.ts;
+
+  if (!aOrder && !bOrder) {
+    return aTs - bTs;
+  }
+
+  if (!bOrder) return -1;
+  if (!aOrder) return 1;
+
+  if (aOrder > bOrder) {
+    return 1;
+  }
+  return 0;
+};
+
 const getFlattenSpaceHierarchy = (
   rootSpaceId: string,
   spaceRooms: Set<string>,
@@ -66,10 +87,9 @@ const getFlattenSpaceHierarchy = (
   };
   findAndCollectHierarchySpaces(rootSpaceItem);
 
-  // TODO: sort by order + added ts
   spaceItems = [
     rootSpaceItem,
-    ...spaceItems.filter((item) => item.roomId !== rootSpaceId).sort((a, b) => a.ts - b.ts),
+    ...spaceItems.filter((item) => item.roomId !== rootSpaceId).sort(hierarchyItemByOrder),
   ];
 
   const hierarchy: HierarchyItem[] = spaceItems.flatMap((spaceItem) => {
@@ -93,7 +113,7 @@ const getFlattenSpaceHierarchy = (
       };
       childItems.push(childItem);
     });
-    return [spaceItem, ...childItems.sort((a, b) => a.ts - b.ts)];
+    return [spaceItem, ...childItems.sort(hierarchyItemByOrder)];
   });
 
   return hierarchy;
diff --git a/src/app/utils/ASCIILexicalTable.ts b/src/app/utils/ASCIILexicalTable.ts
index c9001876..61b2481a 100644
--- a/src/app/utils/ASCIILexicalTable.ts
+++ b/src/app/utils/ASCIILexicalTable.ts
@@ -185,16 +185,53 @@ export class ASCIILexicalTable {
     return undefined;
   }
 
-  between(i: string, j: string): string | undefined {
-    if (!this.has(i) || !this.has(j)) {
+  between(a: string, b: string): string | undefined {
+    if (!this.has(a) || !this.has(b)) {
       return undefined;
     }
 
-    const centerIndex = Math.floor((this.index(i) + this.index(j)) / 2);
+    const centerIndex = Math.floor((this.index(a) + this.index(b)) / 2);
 
-    const b = this.get(centerIndex);
-    if (b === i || b === j) return undefined;
-    return b;
+    const str = this.get(centerIndex);
+    if (str === a || str === b) return undefined;
+    return str;
+  }
+
+  nBetween(n: number, a: string, b: string): string[] | undefined {
+    if (n <= 0 || !this.has(a) || !this.has(b)) {
+      return undefined;
+    }
+
+    const indexA = this.index(a);
+    const indexB = this.index(b);
+
+    const nBetween = Math.max(indexA, indexB) - Math.min(indexA, indexB);
+    if (nBetween < n) {
+      return undefined;
+    }
+    const segmentSize = Math.floor(nBetween / (n + 1));
+    if (segmentSize === 0) return undefined;
+
+    const items: string[] = [];
+
+    for (
+      let segmentIndex = indexA + segmentSize;
+      segmentIndex < indexB;
+      segmentIndex += segmentSize
+    ) {
+      if (items.length === n) break;
+
+      const str = this.get(segmentIndex);
+
+      if (!str) break;
+      items.push(str);
+    }
+
+    if (items.length < n) {
+      return undefined;
+    }
+
+    return items;
   }
 }
 
@@ -234,10 +271,12 @@ export class ASCIILexicalTable {
 
 // console.log('\n');
 
-// const lex = new ASCIILexicalTable('a'.charCodeAt(0), 'c'.charCodeAt(0), 5);
+// const lex = new ASCIILexicalTable('a'.charCodeAt(0), 'c'.charCodeAt(0), 3);
 // printLex(lex);
-// console.log(lex.between('a', 'aacb'));
-// console.log(lex.get(123) === 'baa');
+// console.log(lex.size());
+// console.log(lex.nBetween(8, ' ', '~~~~~'));
+// console.log(lex.between('a', 'ccc'));
+// console.log(lex.get(11));
 // console.log(lex.get(11) === 'aaac');
 
 // const lex4 = new ASCIILexicalTable(' '.charCodeAt(0), '~'.charCodeAt(0), 5);
@@ -291,3 +330,64 @@ export class ASCIILexicalTable {
 // };
 
 // perf();
+
+const findNextFilledKey = (
+  fromIndex: number,
+  keys: Array<string | undefined>
+): [number, string] | [-1, undefined] => {
+  for (let j = fromIndex; j < keys.length; j += 1) {
+    const key = keys[j];
+    if (typeof key === 'string') {
+      return [j, key];
+    }
+  }
+
+  return [-1, undefined];
+};
+
+export const orderKeys = (
+  lex: ASCIILexicalTable,
+  keys: Array<string | undefined>
+): Array<string> | undefined => {
+  const newKeys: string[] = [];
+
+  for (let i = 0; i < keys.length; ) {
+    const key = keys[i];
+    const collectedKeys: string[] = [];
+    const [nextKeyIndex, nextKey] = findNextFilledKey(i + 1, keys);
+    const isKey = typeof key === 'string';
+
+    if (isKey) {
+      collectedKeys.push(key);
+    }
+
+    const keyToGenerateCount =
+      (nextKeyIndex === -1 ? keys.length : nextKeyIndex) - (key ? i + 1 : i + 0);
+
+    if (keyToGenerateCount > 0) {
+      const generatedKeys = lex.nBetween(
+        keyToGenerateCount,
+        key ?? lex.first(),
+        nextKey ?? lex.last()
+      );
+      if (generatedKeys) {
+        collectedKeys.push(...generatedKeys);
+      } else {
+        return lex.nBetween(keys?.length, lex.first(), lex.last());
+      }
+    }
+
+    newKeys.push(...collectedKeys);
+    i += collectedKeys.length;
+  }
+
+  if (newKeys.length !== keys.length) {
+    return undefined;
+  }
+
+  return newKeys;
+};
+
+// const lex = new ASCIILexicalTable('a'.charCodeAt(0), 'b'.charCodeAt(0), 2);
+// const keys = [undefined, undefined];
+// console.log(orderKeys(lex, keys));