diff --git a/runtime/alloc.hpp b/runtime/alloc.hpp
new file mode 100644
index 0000000..9d4e4e3
--- /dev/null
+++ b/runtime/alloc.hpp
@@ -0,0 +1,170 @@
+#pragma once
+
+#include "value.hpp"
+#include <cstddef>
+#include <cstdint>
+#include <optional>
+#include <string>
+#include <unordered_map>
+#include <variant>
+#include <vector>
+
+namespace sliger::heap {
+
+struct Array {
+    std::vector<Value> values;
+};
+
+struct Struct {
+    std::unordered_map<std::string, Value> fields;
+};
+
+enum class AllocType {
+    Value,
+    Array,
+    Struct,
+};
+
+// clang-format off
+template <AllocType type> struct AllocTypeType {};
+template <> struct AllocTypeType<AllocType::Value> { using Type = Value; };
+template <> struct AllocTypeType<AllocType::Array> { using Type = Array; };
+template <> struct AllocTypeType<AllocType::Struct> { using Type = Struct; };
+// clang-format on
+
+struct AllocItem {
+    template <AllocType AT> inline auto as() & -> AllocTypeType<AT>::Type&
+    {
+        return std::get<typename AllocTypeType<AT>::Type>(this->value);
+    }
+    template <AllocType AT>
+    inline auto as() const& -> const AllocTypeType<AT>::Type&
+    {
+        return std::get<typename AllocTypeType<AT>::Type>(this->value);
+    }
+    template <AllocType AT> inline auto as() && -> AllocTypeType<AT>::Type&&
+    {
+        return std::move(
+            std::get<typename AllocTypeType<AT>::Type>(this->value));
+    }
+    template <AllocType AT>
+    inline auto as() const&& -> const AllocTypeType<AT>::Type&&
+    {
+        return std::move(
+            std::get<typename AllocTypeType<AT>::Type>(this->value));
+    }
+
+    AllocType type;
+    std::variant<Value, Array, Struct> value;
+};
+
+enum class ErrType {
+    InvalidPtrAccess,
+    CannotAllocate,
+};
+
+template <typename T> struct Res {
+    Res(T val)
+        : val(std::forward<T>(val))
+    {
+    }
+    Res(ErrType err)
+        : err(err)
+    {
+    }
+
+    std::optional<T> val;
+    std::optional<ErrType> err;
+};
+
+class Heap {
+public:
+    inline auto can_allocate() const -> bool
+    {
+        return this->sel->size() < this->max_size;
+    }
+
+    inline void collect(const std::vector<uint32_t>& ptr_stack_values)
+    {
+        this->other->reserve(this->max_size);
+        for (auto ptr : ptr_stack_values) {
+            move_item_to_other(ptr);
+        }
+        this->sel->clear();
+        std::swap(this->sel, this->other);
+        if (this->sel->size() + 1 >= this->max_size) {
+            this->max_size *= 2;
+            this->sel->reserve(this->max_size);
+        } else if (this->sel->size() * 2 < this->max_size) {
+            this->max_size /= 2;
+            this->sel->shrink_to_fit();
+            this->sel->reserve(this->max_size);
+        }
+    }
+
+    inline auto at(uint32_t ptr) -> Res<AllocItem*>
+    {
+        if (ptr >= this->sel->size()) {
+            return ErrType::InvalidPtrAccess;
+        }
+        return &this->sel->at(ptr);
+    }
+
+    template <AllocType type> auto alloc() -> Res<uint32_t>
+    {
+        if (not can_allocate()) {
+            return ErrType::CannotAllocate;
+        }
+        auto ptr = static_cast<uint32_t>(this->sel->size());
+        this->sel->push_back(typename AllocTypeType<type>::Type {});
+        return ptr;
+    }
+
+private:
+    inline void move_item_to_other(uint32_t ptr)
+    {
+        auto res = at(ptr);
+        if (!res.val.has_value())
+            return;
+        auto val = res.val.value();
+        switch (val->type) {
+            case AllocType::Value: {
+                auto& v = val->as<AllocType::Value>();
+                if (v.type() == ValueType::Ptr) {
+                    move_item_to_other(v.template as<ValueType::Ptr>().value);
+                }
+                break;
+            }
+            case AllocType::Array: {
+                auto& vs = val->as<AllocType::Array>();
+                for (auto& v : vs.values) {
+                    if (v.type() == ValueType::Ptr) {
+                        move_item_to_other(
+                            v.template as<ValueType::Ptr>().value);
+                    }
+                }
+                break;
+            }
+            case AllocType::Struct: {
+                auto& vs = val->as<AllocType::Struct>();
+                for (auto& [key, v] : vs.fields) {
+                    if (v.type() == ValueType::Ptr) {
+                        move_item_to_other(
+                            v.template as<ValueType::Ptr>().value);
+                    }
+                }
+                break;
+            }
+        }
+    }
+
+    size_t max_size = 4;
+
+    std::vector<AllocItem> heap_1;
+    std::vector<AllocItem> heap_2;
+
+    std::vector<AllocItem>* sel = &heap_1;
+    std::vector<AllocItem>* other = &heap_2;
+};
+
+}
diff --git a/runtime/vm.hpp b/runtime/vm.hpp
index 0fadee4..0ade960 100644
--- a/runtime/vm.hpp
+++ b/runtime/vm.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "alloc.hpp"
 #include "arch.hpp"
 #include "json.hpp"
 #include "value.hpp"
@@ -271,7 +272,7 @@ private:
     const uint32_t* program;
     size_t program_size;
     std::vector<Value> stack;
-    std::vector<Value> pool_heap;
+    heap::Heap heap;
     SourcePos current_pos = { 0, 1, 1 };
     int64_t instruction_counter = 0;
 
diff --git a/surveys/code_coverage/.vscode/settings.json b/surveys/code_coverage/.vscode/settings.json
new file mode 100644
index 0000000..2c7ddc5
--- /dev/null
+++ b/surveys/code_coverage/.vscode/settings.json
@@ -0,0 +1,5 @@
+{
+    "deno.enable": true,
+    "deno.lint": true,
+    "deno.unstable": true
+}
\ No newline at end of file
diff --git a/web/main.ts b/web/main.ts
index 6313814..e3ad97d 100644
--- a/web/main.ts
+++ b/web/main.ts
@@ -22,7 +22,7 @@ async function compileProgram(filepath: string) {
     const result = await compiler.compileWithDebug(filepath);
 }
 
-async function runProgramWithDebug(program: string) {
+async function runProgramWithDebug(program: number[]) {
     const connection = await runtime.connect();
     connection.send({
         type: "run-debug",