diff --git a/charming/src/element/mod.rs b/charming/src/element/mod.rs
index 14ed0b6..69819ab 100644
--- a/charming/src/element/mod.rs
+++ b/charming/src/element/mod.rs
@@ -36,6 +36,7 @@ pub mod pointer;
 pub mod scale_limit;
 pub mod select;
 pub mod shape;
+pub mod smoothness;
 pub mod sort;
 pub mod split_area;
 pub mod split_line;
diff --git a/charming/src/element/smoothness.rs b/charming/src/element/smoothness.rs
new file mode 100644
index 0000000..24fac82
--- /dev/null
+++ b/charming/src/element/smoothness.rs
@@ -0,0 +1,36 @@
+use serde::Serialize;
+
+pub enum Smoothness {
+    Single(f64),
+    Boolean(bool),
+}
+
+impl Serialize for Smoothness {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        match self {
+            Smoothness::Single(smoothness) => serializer.serialize_f64(*smoothness),
+            Smoothness::Boolean(smoothness) => serializer.serialize_bool(*smoothness),
+        }
+    }
+}
+
+impl From<f64> for Smoothness {
+    fn from(smoothness: f64) -> Self {
+        Smoothness::Single(smoothness)
+    }
+}
+
+impl From<i64> for Smoothness {
+    fn from(smoothness: i64) -> Self {
+        Smoothness::Single(smoothness as f64)
+    }
+}
+
+impl From<bool> for Smoothness {
+    fn from(smoothness: bool) -> Self {
+        Smoothness::Boolean(smoothness)
+    }
+}
diff --git a/charming/src/series/line.rs b/charming/src/series/line.rs
index aff6409..9338ccd 100644
--- a/charming/src/series/line.rs
+++ b/charming/src/series/line.rs
@@ -3,8 +3,8 @@ use serde::Serialize;
 use crate::{
     datatype::{DataFrame, DataPoint},
     element::{
-        AreaStyle, CoordinateSystem, DimensionEncode, Emphasis, ItemStyle, Label, LineStyle,
-        MarkArea, MarkLine, MarkPoint, Symbol,
+        smoothness::Smoothness, AreaStyle, CoordinateSystem, DimensionEncode, Emphasis, ItemStyle,
+        Label, LineStyle, MarkArea, MarkLine, MarkPoint, Symbol,
     },
 };
 
@@ -51,7 +51,7 @@ pub struct Line {
     emphasis: Option<Emphasis>,
 
     #[serde(skip_serializing_if = "Option::is_none")]
-    smooth: Option<f64>,
+    smooth: Option<Smoothness>,
 
     #[serde(skip_serializing_if = "Option::is_none")]
     mark_point: Option<MarkPoint>,
@@ -174,7 +174,7 @@ impl Line {
     }
 
     /// Smoothness.
-    pub fn smooth<F: Into<f64>>(mut self, smooth: F) -> Self {
+    pub fn smooth<F: Into<Smoothness>>(mut self, smooth: F) -> Self {
         self.smooth = Some(smooth.into());
         self
     }
diff --git a/charming/src/series/parallel.rs b/charming/src/series/parallel.rs
index 0754b5d..f129613 100644
--- a/charming/src/series/parallel.rs
+++ b/charming/src/series/parallel.rs
@@ -2,7 +2,7 @@ use serde::Serialize;
 
 use crate::{
     datatype::{DataFrame, DataPoint},
-    element::{ColorBy, CoordinateSystem, Emphasis, LineStyle},
+    element::{smoothness::Smoothness, ColorBy, CoordinateSystem, Emphasis, LineStyle},
 };
 
 #[derive(Serialize)]
@@ -49,7 +49,7 @@ pub struct Parallel {
     realtime: Option<bool>,
 
     #[serde(skip_serializing_if = "Option::is_none")]
-    smooth: Option<f64>,
+    smooth: Option<Smoothness>,
 
     #[serde(skip_serializing_if = "Option::is_none")]
     progressive: Option<f64>,
@@ -142,7 +142,7 @@ impl Parallel {
         self
     }
 
-    pub fn smooth<F: Into<f64>>(mut self, smooth: F) -> Self {
+    pub fn smooth<F: Into<Smoothness>>(mut self, smooth: F) -> Self {
         self.smooth = Some(smooth.into());
         self
     }