diff --git a/app/src/main/java/me/ash/reader/ui/extension/ColorScheme.kt b/app/src/main/java/me/ash/reader/ui/extension/ColorScheme.kt
new file mode 100644
index 0000000..6ff4f0c
--- /dev/null
+++ b/app/src/main/java/me/ash/reader/ui/extension/ColorScheme.kt
@@ -0,0 +1,16 @@
+package me.ash.reader.ui.extension
+
+import androidx.compose.material3.ColorScheme
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.compositeOver
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.dp
+import kotlin.math.ln
+
+fun ColorScheme.surfaceColorAtElevation(
+    elevation: Dp,
+): Color {
+    if (elevation == 0.dp) return surface
+    val alpha = ((4.5f * ln(elevation.value + 1)) + 2f) / 100f
+    return primary.copy(alpha = alpha).compositeOver(surface)
+}
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