diff --git a/color-module/src/lib.rs b/color-module/src/lib.rs
index 6f8c944..429f3c7 100644
--- a/color-module/src/lib.rs
+++ b/color-module/src/lib.rs
@@ -95,8 +95,10 @@ pub fn represent_hct(color: &str) -> Result<Box<[f32]>, errors::ColorError> {
     let origin_color = Srgb::from_str(color)
         .map_err(|_| errors::ColorError::UnrecogniazedRGB(color.to_string()))?
         .into_format::<f32>();
-    let extra_parameters = Parameters::default_static_wp(40.0);
-    let hct = Cam16Jch::from_xyz(origin_color.into_color(), extra_parameters);
+    let hct = Cam16Jch::from_xyz(
+        origin_color.into_color(),
+        Parameters::default_static_wp(40.0),
+    );
     Ok(Box::new([
         hct.hue.into_positive_degrees(),
         hct.chroma,
@@ -106,9 +108,8 @@ pub fn represent_hct(color: &str) -> Result<Box<[f32]>, errors::ColorError> {
 
 #[wasm_bindgen]
 pub fn hct_to_hex(hue: f32, chroma: f32, tone: f32) -> Result<String, errors::ColorError> {
-    let extra_parameters = Parameters::default_static_wp(40.0);
     let hct = Cam16Jch::new(tone, chroma, hue);
-    let srgb = Srgb::from_color_unclamped(hct.into_xyz(extra_parameters));
+    let srgb = Srgb::from_color_unclamped(hct.into_xyz(Parameters::default_static_wp(40.0)));
     if !srgb.is_within_bounds() {
         return Err(errors::ColorError::ComponentOutOfBounds);
     }
@@ -324,3 +325,54 @@ pub fn series(
     }
     Ok(color_series)
 }
+
+#[wasm_bindgen]
+pub fn tonal_lighten_series(
+    color: &str,
+    expand_amount: i16,
+    step: f32,
+) -> Result<Vec<String>, errors::ColorError> {
+    let origin_color = Srgb::from_str(color)
+        .map_err(|_| errors::ColorError::UnrecogniazedRGB(color.to_string()))?
+        .into_format::<f32>();
+    let hct = Cam16Jch::from_xyz(
+        origin_color.into_color(),
+        Parameters::default_static_wp(40.0),
+    );
+
+    let mut color_series = Vec::new();
+    let mut lightness = hct.lightness;
+    for _ in 1..=expand_amount {
+        lightness += (1.0 - lightness) * step;
+        let lightened_color = Cam16Jch::new(lightness, hct.chroma, hct.hue);
+        let srgb = Srgb::from_color(lightened_color.into_xyz(Parameters::default_static_wp(40.0)));
+        color_series.push(format!("{:x}", srgb.into_format::<u8>()));
+    }
+
+    Ok(color_series.into_iter().rev().collect())
+}
+
+pub fn tonal_darken_series(
+    color: &str,
+    expand_amount: i16,
+    step: f32,
+) -> Result<Vec<String>, errors::ColorError> {
+    let origin_color = Srgb::from_str(color)
+        .map_err(|_| errors::ColorError::UnrecogniazedRGB(color.to_string()))?
+        .into_format::<f32>();
+    let hct = Cam16Jch::from_xyz(
+        origin_color.into_color(),
+        Parameters::default_static_wp(40.0),
+    );
+
+    let mut color_series = Vec::new();
+    let mut lightness = hct.lightness;
+    for _ in 1..=expand_amount {
+        lightness *= step;
+        let darkened_color = Cam16Jch::new(lightness, hct.chroma, hct.hue);
+        let srgb = Srgb::from_color(darkened_color.into_xyz(Parameters::default_static_wp(40.0)));
+        color_series.push(format!("{:x}", srgb.into_format::<u8>()));
+    }
+
+    Ok(color_series)
+}