diff --git a/src/observer/topic.gleam b/src/observer/topic.gleam
new file mode 100644
index 0000000..3b11cfa
--- /dev/null
+++ b/src/observer/topic.gleam
@@ -0,0 +1,206 @@
+import gleam/dict
+import gleam/list
+import observer
+
+type TopicValue(value_type) {
+  TopicValue(topics: List(String), value: value_type)
+}
+
+pub opaque type Hub(value_type) {
+  Hub(inner: observer.Hub(TopicValue(value_type)))
+}
+
+fn has_intersection(a: List(String), b: List(String)) -> Bool {
+  let #(smaller, larger) = case list.length(a) > list.length(b) {
+    True -> #(a, b)
+    False -> #(b, a)
+  }
+
+  let smaller = dict.from_list(list.map(smaller, fn(topic) { #(topic, Nil) }))
+  list.any(larger, fn(topic) { dict.has_key(smaller, topic) })
+}
+
+pub fn new(in context: fn(Hub(value_type)) -> result) -> result {
+  use inner <- observer.new()
+  let hub = Hub(inner)
+
+  context(hub)
+}
+
+pub fn notify(
+  on hub: Hub(value_type),
+  and topics: List(String),
+  with value: value_type,
+) -> Nil {
+  observer.notify(hub.inner, TopicValue(topics, value))
+}
+
+pub fn subscribe(
+  on hub: Hub(value_type),
+  and topics: List(String),
+  with callback: observer.Callback(value_type),
+) -> observer.Unsubscribe {
+  use value <- observer.subscribe(hub.inner)
+  let TopicValue(message_topics, value) = value
+
+  case has_intersection(topics, message_topics) {
+    True -> callback(value)
+    False -> Nil
+  }
+}
+
+type TopicValue2(value_type) {
+  TopicValue2(topics1: List(String), topics2: List(String), value: value_type)
+}
+
+pub opaque type Hub2(value_type) {
+  Hub2(inner: observer.Hub(TopicValue2(value_type)))
+}
+
+pub fn new2(in context: fn(Hub2(value_type)) -> result) -> result {
+  use inner <- observer.new()
+  let hub = Hub2(inner)
+
+  context(hub)
+}
+
+pub fn notify2(
+  hub: Hub2(value_type),
+  topics1: List(String),
+  topics2: List(String),
+  value: value_type,
+) -> Nil {
+  observer.notify(hub.inner, TopicValue2(topics1, topics2, value))
+}
+
+pub fn subscribe2(
+  hub: Hub2(value_type),
+  topics1: List(String),
+  topics2: List(String),
+  callback: observer.Callback(value_type),
+) -> observer.Unsubscribe {
+  use value <- observer.subscribe(hub.inner)
+  let TopicValue2(message_topics1, message_topics2, value) = value
+
+  case
+    has_intersection(topics1, message_topics1)
+    && has_intersection(topics2, message_topics2)
+  {
+    True -> callback(value)
+    False -> Nil
+  }
+}
+
+type TopicValue3(value_type) {
+  TopicValue3(
+    topics1: List(String),
+    topics2: List(String),
+    topics3: List(String),
+    value: value_type,
+  )
+}
+
+pub opaque type Hub3(value_type) {
+  Hub3(inner: observer.Hub(TopicValue3(value_type)))
+}
+
+pub fn new3(in context: fn(Hub3(value_type)) -> result) -> result {
+  use inner <- observer.new()
+  let hub = Hub3(inner)
+
+  context(hub)
+}
+
+pub fn notify3(
+  hub: Hub3(value_type),
+  topics1: List(String),
+  topics2: List(String),
+  topics3: List(String),
+  value: value_type,
+) -> Nil {
+  observer.notify(hub.inner, TopicValue3(topics1, topics2, topics3, value))
+}
+
+pub fn subscribe3(
+  hub: Hub3(value_type),
+  topics1: List(String),
+  topics2: List(String),
+  topics3: List(String),
+  callback: observer.Callback(value_type),
+) -> observer.Unsubscribe {
+  use value <- observer.subscribe(hub.inner)
+  let TopicValue3(message_topics1, message_topics2, message_topics3, value) =
+    value
+
+  case
+    has_intersection(topics1, message_topics1)
+    && has_intersection(topics2, message_topics2)
+    && has_intersection(topics3, message_topics3)
+  {
+    True -> callback(value)
+    False -> Nil
+  }
+}
+
+pub opaque type TopicValue4(value_type) {
+  TopicValue4(
+    topics1: List(String),
+    topics2: List(String),
+    topics3: List(String),
+    topics4: List(String),
+    value: value_type,
+  )
+}
+
+pub opaque type Hub4(value_type) {
+  Hub4(inner: observer.Hub(TopicValue4(value_type)))
+}
+
+pub fn new4(in context: fn(Hub4(value_type)) -> result) -> result {
+  use inner <- observer.new()
+  let hub = Hub4(inner)
+
+  context(hub)
+}
+
+pub fn notify4(
+  hub: Hub4(value_type),
+  topics1: List(String),
+  topics2: List(String),
+  topics3: List(String),
+  topics4: List(String),
+  value: value_type,
+) -> Nil {
+  observer.notify(
+    hub.inner,
+    TopicValue4(topics1, topics2, topics3, topics4, value),
+  )
+}
+
+pub fn subscribe4(
+  hub: Hub4(value_type),
+  topics1: List(String),
+  topics2: List(String),
+  topics3: List(String),
+  topics4: List(String),
+  callback: observer.Callback(value_type),
+) -> observer.Unsubscribe {
+  use value <- observer.subscribe(hub.inner)
+  let TopicValue4(
+    message_topics1,
+    message_topics2,
+    message_topics3,
+    message_topics4,
+    value,
+  ) = value
+
+  case
+    has_intersection(topics1, message_topics1)
+    && has_intersection(topics2, message_topics2)
+    && has_intersection(topics3, message_topics3)
+    && has_intersection(topics4, message_topics4)
+  {
+    True -> callback(value)
+    False -> Nil
+  }
+}