diff --git a/src/Library/CreatureData/LearnableAttacks.cpp b/src/Library/CreatureData/LearnableAttacks.cpp
index 863cceb..effce02 100644
--- a/src/Library/CreatureData/LearnableAttacks.cpp
+++ b/src/Library/CreatureData/LearnableAttacks.cpp
@@ -1,13 +1,68 @@
 #include "LearnableAttacks.hpp"
 
-using namespace CreatureLib::Library;
+namespace CreatureLib::Library {
+    struct LearnableAttacks::impl {
+    private:
+        ArbUt::Dictionary<uint8_t, ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>> _learnedByLevel;
+        ArbUt::List<ArbUt::BorrowedPtr<const AttackData>> _distinctLevelAttacks;
 
-void LearnableAttacks::AddLevelAttack(level_int_t level, ArbUt::BorrowedPtr<const AttackData> attack) {
-    if (_learnedByLevel.Has(level)) {
-        _learnedByLevel[level].Append(attack);
-    } else {
-        _learnedByLevel.Insert(level, {attack});
+    public:
+        explicit impl(size_t levelAttackCapacity)
+            : _learnedByLevel(
+                  ArbUt::Dictionary<uint8_t, ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>>(levelAttackCapacity)) {}
+
+        ~impl() = default;
+
+        void AddLevelAttack(level_int_t level, const ArbUt::BorrowedPtr<const AttackData>& attack) {
+            if (_learnedByLevel.Has(level)) {
+                _learnedByLevel[level].Append(attack);
+            } else {
+                _learnedByLevel.Insert(level, {attack});
+            }
+            if (!_distinctLevelAttacks.Contains(attack)) {
+                _distinctLevelAttacks.Append(attack);
+            }
+        }
+
+        inline bool HasAttacksForLevel(uint8_t level) const noexcept { return _learnedByLevel.Has(level); }
+        inline const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& GetAttacksForLevel(uint8_t level) const {
+            if (!_learnedByLevel.Has(level)) {
+                THROW("No attacks found for level " << (uint32_t)level << ".");
+            }
+            return _learnedByLevel.Get(level);
+        }
+
+        inline const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& GetDistinctLevelAttacks() const noexcept {
+            return _distinctLevelAttacks;
+        }
+
+        ArbUt::BorrowedPtr<const AttackData> GetRandomAttack(ArbUt::Random& rand) const {
+            if (_distinctLevelAttacks.Count() == 0) {
+                return nullptr;
+            }
+            auto val = rand.Get(_distinctLevelAttacks.Count());
+            auto it = _distinctLevelAttacks.begin();
+            std::advance(it, val);
+            return *it;
+        }
+    };
+
+    LearnableAttacks::LearnableAttacks(size_t levelAttackCapacity) : _impl(new impl(levelAttackCapacity)) {}
+    LearnableAttacks::~LearnableAttacks() = default;
+
+    void LearnableAttacks::AddLevelAttack(level_int_t level, ArbUt::BorrowedPtr<const AttackData> attack) {
+        _impl->AddLevelAttack(level, attack);
     }
-    if (!_distinctLevelAttacks.Contains(attack))
-        _distinctLevelAttacks.Append(attack);
+    bool LearnableAttacks::HasAttacksForLevel(uint8_t level) const noexcept { return _impl->HasAttacksForLevel(level); }
+    const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& LearnableAttacks::GetAttacksForLevel(uint8_t level) const {
+        return _impl->GetAttacksForLevel(level);
+    }
+    const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>&
+    LearnableAttacks::GetDistinctLevelAttacks() const noexcept {
+        return _impl->GetDistinctLevelAttacks();
+    }
+    ArbUt::BorrowedPtr<const AttackData> LearnableAttacks::GetRandomAttack(ArbUt::Random& rand) const {
+        return _impl->GetRandomAttack(rand);
+    }
+
 }
\ No newline at end of file
diff --git a/src/Library/CreatureData/LearnableAttacks.hpp b/src/Library/CreatureData/LearnableAttacks.hpp
index 060322e..7c9a418 100644
--- a/src/Library/CreatureData/LearnableAttacks.hpp
+++ b/src/Library/CreatureData/LearnableAttacks.hpp
@@ -2,45 +2,23 @@
 #define CREATURELIB_LEARNABLEATTACKS_HPP
 
 #include <Arbutils/Random.hpp>
-#include "../../Defines.hpp"
 #include "../Attacks/AttackData.hpp"
 
 namespace CreatureLib::Library {
     class LearnableAttacks {
-    protected:
-        ArbUt::Dictionary<uint8_t, ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>> _learnedByLevel;
-        ArbUt::List<ArbUt::BorrowedPtr<const AttackData>> _distinctLevelAttacks;
+    private:
+        struct impl;
+        std::unique_ptr<impl> _impl;
 
     public:
-        explicit LearnableAttacks(size_t levelAttackCapacity)
-            : _learnedByLevel(
-                  ArbUt::Dictionary<uint8_t, ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>>(levelAttackCapacity)) {}
-
-        virtual ~LearnableAttacks() = default;
+        explicit LearnableAttacks(size_t levelAttackCapacity);
+        virtual ~LearnableAttacks();
 
         void AddLevelAttack(level_int_t level, ArbUt::BorrowedPtr<const AttackData> attack);
-
-        inline bool HasAttacksForLevel(uint8_t level) const noexcept { return _learnedByLevel.Has(level); }
-        inline const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& GetAttacksForLevel(uint8_t level) const {
-            if (!_learnedByLevel.Has(level)) {
-                THROW("No attacks found for level " << (uint32_t)level << ".");
-            }
-            return _learnedByLevel.Get(level);
-        }
-
-        inline const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& GetDistinctLevelAttacks() const noexcept {
-            return _distinctLevelAttacks;
-        }
-
-        virtual ArbUt::BorrowedPtr<const AttackData> GetRandomAttack(ArbUt::Random& rand) const {
-            if (_distinctLevelAttacks.Count() == 0) {
-                return nullptr;
-            }
-            auto val = rand.Get(_distinctLevelAttacks.Count());
-            auto it = _distinctLevelAttacks.begin();
-            std::advance(it, val);
-            return *it;
-        }
+        bool HasAttacksForLevel(uint8_t level) const noexcept;
+        const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& GetAttacksForLevel(uint8_t level) const;
+        const ArbUt::List<ArbUt::BorrowedPtr<const AttackData>>& GetDistinctLevelAttacks() const noexcept;
+        virtual ArbUt::BorrowedPtr<const AttackData> GetRandomAttack(ArbUt::Random& rand) const;
     };
 }
 
diff --git a/src/Library/GrowthRates/LookupGrowthRate.hpp b/src/Library/GrowthRates/LookupGrowthRate.hpp
index 1050133..e8d8e4c 100644
--- a/src/Library/GrowthRates/LookupGrowthRate.hpp
+++ b/src/Library/GrowthRates/LookupGrowthRate.hpp
@@ -12,7 +12,7 @@ namespace CreatureLib::Library {
         LookupGrowthRate(const ArbUt::List<uint32_t>& experience) : _experience(experience) {}
 
         level_int_t CalculateLevel(uint32_t experience) const override {
-            for (level_int_t i = 0; i < _experience.Count(); i++) {
+            for (level_int_t i = 0; i < (level_int_t)_experience.Count(); i++) {
                 if (_experience[i] > experience) {
                     return i;
                 }
diff --git a/src/Precompiled.hxx b/src/Precompiled.hxx
index 5a08e73..e76726c 100644
--- a/src/Precompiled.hxx
+++ b/src/Precompiled.hxx
@@ -30,4 +30,7 @@
 #include <Arbutils/Memory/UniquePtrList.hpp>
 #include <Arbutils/StringView.hpp>
 
+// CreatureLib
+#include "Defines.hpp"
+
 #endif // CREATURELIB_PRECOMPILED_HXX