diff --git a/README.md b/README.md
index f747eca..9d9b998 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,11 @@ Build a simple key-value storage engine in a week!
 The tutorial is available at [https://skyzh.github.io/mini-lsm](https://skyzh.github.io/mini-lsm). You can use the provided starter
 code to kick off your project, and follow the tutorial to implement the LSM tree.
 
-Join the mini-lsm community: [![Join skyzh's Discord Server](https://dcbadge.vercel.app/api/server/ZgXzxpua3H)](https://skyzh.dev/join/discord)
+## Community
+
+You may join skyzh's Discord server and study with the mini-lsm community.
+
+[![Join skyzh's Discord Server](https://dcbadge.vercel.app/api/server/ZgXzxpua3H)](https://skyzh.dev/join/discord)
 
 ## Development
 
diff --git a/mini-lsm-week-1/src/lsm_storage.rs b/mini-lsm-week-1/src/lsm_storage.rs
index a55bba0..f57e189 100644
--- a/mini-lsm-week-1/src/lsm_storage.rs
+++ b/mini-lsm-week-1/src/lsm_storage.rs
@@ -218,6 +218,9 @@ impl LsmStorage {
 
         let iter = TwoMergeIterator::create(memtable_iter, table_iter)?;
 
-        Ok(FusedIterator::new(LsmIterator::new(iter, map_bound(upper))?))
+        Ok(FusedIterator::new(LsmIterator::new(
+            iter,
+            map_bound(upper),
+        )?))
     }
 }
diff --git a/mini-lsm/src/compact.rs b/mini-lsm/src/compact.rs
index 22e9573..1ac9487 100644
--- a/mini-lsm/src/compact.rs
+++ b/mini-lsm/src/compact.rs
@@ -37,7 +37,9 @@ impl LsmStorage {
         let mut iters = Vec::new();
         iters.reserve(tables.len());
         for table in tables.iter() {
-            iters.push(Box::new(SsTableIterator::create_and_seek_to_first(table.clone())?));
+            iters.push(Box::new(SsTableIterator::create_and_seek_to_first(
+                table.clone(),
+            )?));
         }
         let mut iter = MergeIterator::create(iters);
 
diff --git a/mini-lsm/src/compact/leveled.rs b/mini-lsm/src/compact/leveled.rs
index ab64678..ad854c7 100644
--- a/mini-lsm/src/compact/leveled.rs
+++ b/mini-lsm/src/compact/leveled.rs
@@ -166,17 +166,16 @@ impl LeveledCompactionController {
             .copied()
             .collect::<HashSet<_>>();
         if let Some(upper_level) = task.upper_level {
-            let new_upper_level_ssts =
-                snapshot.levels[upper_level - 1]
-                    .1
-                    .iter()
-                    .filter_map(|x| {
-                        if upper_level_sst_ids_set.remove(x) {
-                            return None;
-                        }
-                        Some(*x)
-                    })
-                    .collect::<Vec<_>>();
+            let new_upper_level_ssts = snapshot.levels[upper_level - 1]
+                .1
+                .iter()
+                .filter_map(|x| {
+                    if upper_level_sst_ids_set.remove(x) {
+                        return None;
+                    }
+                    Some(*x)
+                })
+                .collect::<Vec<_>>();
             assert!(upper_level_sst_ids_set.is_empty());
             snapshot.levels[upper_level - 1].1 = new_upper_level_ssts;
         } else {
diff --git a/mini-lsm/src/lsm_storage.rs b/mini-lsm/src/lsm_storage.rs
index 2bcf69c..a6e8595 100644
--- a/mini-lsm/src/lsm_storage.rs
+++ b/mini-lsm/src/lsm_storage.rs
@@ -223,6 +223,9 @@ impl LsmStorage {
 
         let iter = TwoMergeIterator::create(memtable_iter, table_iter)?;
 
-        Ok(FusedIterator::new(LsmIterator::new(iter, map_bound(upper))?))
+        Ok(FusedIterator::new(LsmIterator::new(
+            iter,
+            map_bound(upper),
+        )?))
     }
 }