diff --git a/color-module/src/schemes/swatch_style/swatch.rs b/color-module/src/schemes/swatch_style/swatch.rs
index a445cec..e90e392 100644
--- a/color-module/src/schemes/swatch_style/swatch.rs
+++ b/color-module/src/schemes/swatch_style/swatch.rs
@@ -24,28 +24,26 @@ impl Swatch {
         }
     }
 
-    fn find_interval(&self) -> (usize, usize) {
+    fn find_interval(&self) -> usize {
         if !self.include_primary {
-            return (0, 0);
+            return 0;
         }
         if self.primary_key.l == self.min_key {
-            return (0, 1);
+            return 0;
         }
         if self.primary_key.l == self.max_key {
-            return (self.color_amount - 2, self.color_amount - 1);
+            return self.color_amount - 1;
         }
         let step = (self.max_key - self.min_key) / (self.color_amount - 1) as f32;
-        let index = ((self.primary_key.l - self.min_key) / step) as usize;
-
-        (index, index + 1)
+        ((self.primary_key.l - self.min_key) / step).ceil() as usize
     }
 
     pub fn swatch(&self) -> Vec<Oklch> {
         let mut swatch = Vec::new();
         if self.include_primary {
-            let (_, primary_index) = self.find_interval();
+            let primary_index = self.find_interval();
             if primary_index > 0 {
-                let step = (self.max_key - self.min_key) / primary_index as f32;
+                let step = (self.primary_key.l - self.min_key) / (primary_index - 1) as f32;
                 for i in 0..primary_index {
                     let lightness = self.min_key + step * i as f32;
                     swatch.push(Oklch {
@@ -55,8 +53,8 @@ impl Swatch {
                 }
             }
             if primary_index < self.color_amount - 1 {
-                let step =
-                    (self.max_key - self.min_key) / (self.color_amount - primary_index) as f32;
+                let step = (self.max_key - self.primary_key.l)
+                    / (self.color_amount - primary_index - 1) as f32;
                 for i in primary_index..self.color_amount {
                     let lightness = self.min_key + step * i as f32;
                     swatch.push(Oklch {
diff --git a/src/color_functions/color_module_bg.wasm b/src/color_functions/color_module_bg.wasm
index 64de917..615a4ff 100644
Binary files a/src/color_functions/color_module_bg.wasm and b/src/color_functions/color_module_bg.wasm differ