diff --git a/include/spaic-css/CSS.hpp b/include/spaic-css/CSS.hpp
index f661ea1..708594f 100644
--- a/include/spaic-css/CSS.hpp
+++ b/include/spaic-css/CSS.hpp
@@ -5,9 +5,9 @@
 namespace spaic::css
 {
 template <typename... T>
-Stylesheet css(T... params);
+Stylesheet css(T&&... params);
 template <typename... T>
-Stylesheet keyframes(T... params);
+Stylesheet keyframes(T&&... params);
 } // namespace spaic::css
 
 #include <spaic-css/detail/CSS.hpp>
\ No newline at end of file
diff --git a/include/spaic-css/CssProperty.hpp b/include/spaic-css/CssProperty.hpp
index 12f6093..4a7b2d2 100644
--- a/include/spaic-css/CssProperty.hpp
+++ b/include/spaic-css/CssProperty.hpp
@@ -11,7 +11,8 @@ template <typename T>
 class CssProperty
 {
 public:
-    AssignedCssProperty<T> operator=(T value);
+    template <typename U>
+    AssignedCssProperty<T> operator=(U&& value);
 };
 } // namespace spaic::css::prop
 
diff --git a/include/spaic-css/Unit.hpp b/include/spaic-css/Unit.hpp
index 0ea99c0..06c7599 100644
--- a/include/spaic-css/Unit.hpp
+++ b/include/spaic-css/Unit.hpp
@@ -58,7 +58,7 @@ class CssUnit
     long double value;
 
 public:
-    CssUnit(long double value) noexcept : value(value) {}
+    CssUnit(long double value) noexcept;
 
     std::string toCssValue();
 };
@@ -99,4 +99,6 @@ defineUnitUDL(percent);
 } // namespace spaic::css::unit
 
 #undef defineUnitUDLRaw
-#undef defineUnitUDL
\ No newline at end of file
+#undef defineUnitUDL
+
+#include <spaic-css/detail/Unit.hpp>
\ No newline at end of file
diff --git a/include/spaic-css/detail/CSS.hpp b/include/spaic-css/detail/CSS.hpp
index cb4640e..bde1c6a 100644
--- a/include/spaic-css/detail/CSS.hpp
+++ b/include/spaic-css/detail/CSS.hpp
@@ -5,9 +5,15 @@
 namespace spaic::css
 {
 template <typename... T>
-Stylesheet css(T... params)
+Stylesheet css(T&&... params)
 {
     // TODO: css(params)
     return Stylesheet();
 }
+template<typename ...T>
+Stylesheet keyframes(T&&... params)
+{
+    // TODO: keyframes(params)
+    return Stylesheet();
+}
 } // namespace spaic::css
diff --git a/include/spaic-css/detail/CssProperty.hpp b/include/spaic-css/detail/CssProperty.hpp
index 09fa61e..fd8947c 100644
--- a/include/spaic-css/detail/CssProperty.hpp
+++ b/include/spaic-css/detail/CssProperty.hpp
@@ -4,11 +4,10 @@
 
 namespace spaic::css::prop
 {
-
 template <typename T>
-AssignedCssProperty<T> CssProperty<T>::operator=(T value)
+template <typename U>
+AssignedCssProperty<T> CssProperty<T>::operator=(U&& value)
 {
     return AssignedCssProperty<T>();
 }
-
 } // namespace spaic::css::prop
\ No newline at end of file
diff --git a/include/spaic-css/detail/Unit.hpp b/include/spaic-css/detail/Unit.hpp
new file mode 100644
index 0000000..5787d1d
--- /dev/null
+++ b/include/spaic-css/detail/Unit.hpp
@@ -0,0 +1,9 @@
+#pragma once
+
+#include <spaic-css/Unit.hpp>
+
+namespace spaic::css::unit
+{
+    template <CssUnitType T>
+    CssUnit<T>::CssUnit(long double value) noexcept : value(value) {}
+} // namespace spaic::css::unit