diff --git a/color-module/src/lib.rs b/color-module/src/lib.rs
index bb9c464..cf658bd 100644
--- a/color-module/src/lib.rs
+++ b/color-module/src/lib.rs
@@ -343,15 +343,16 @@ pub fn tonal_lighten_series(
     let mut color_series = Vec::new();
     let mut lightness = hct.lightness;
     for _ in 1..=expand_amount {
-        lightness += (1.0 - lightness) * step;
+        lightness += (100.0 - 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())
+    Ok(color_series)
 }
 
+#[wasm_bindgen]
 pub fn tonal_darken_series(
     color: &str,
     expand_amount: i16,
@@ -368,11 +369,11 @@ pub fn tonal_darken_series(
     let mut color_series = Vec::new();
     let mut lightness = hct.lightness;
     for _ in 1..=expand_amount {
-        lightness *= step;
+        lightness *= 1.0 - 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)
+    Ok(color_series.into_iter().rev().collect())
 }