diff --git a/tests/zecsy.cpp b/tests/zecsy.cpp
index ffb589a..faee0e0 100644
--- a/tests/zecsy.cpp
+++ b/tests/zecsy.cpp
@@ -1,7 +1,14 @@
+#include <catch2/catch_test_macros.hpp>
 #define CATCH_CONFIG_MAIN
 #include <catch2/catch_all.hpp>
+#include "../zecsy.hpp"
 
-TEST_CASE("dumb")
+using namespace zecsy;
+
+TEST_CASE("Create a single entity and verify its existence")
 {
-    REQUIRE(true);
+    world w;
+    
+    auto e = w.make_entity();
+    REQUIRE(w.is_alive(e));
 }
diff --git a/zecsy.hpp b/zecsy.hpp
index 863f475..abefeab 100644
--- a/zecsy.hpp
+++ b/zecsy.hpp
@@ -1,2 +1,45 @@
-//oh hi
-int foo() {}
+#pragma once
+#include <cstdint>
+#include <bitset>
+#include <numeric>
+
+#ifndef MAX_ZECSY_ENTITIES
+    #define MAX_ZECSY_ENTITIES 65536
+#endif // !MAX_ZECSY_ENTITIES
+
+
+namespace zecsy 
+{
+    using entity_id = uint64_t;
+
+    class world final
+    {
+    public:
+        world() = default;
+        world(const world &) = default;
+        world(world &&) = default;
+        world &operator=(const world &) = default;
+        world &operator=(world &&) = default;
+   
+        entity_id make_entity();
+        bool is_alive(entity_id e) const; 
+    private:
+        std::bitset<MAX_ZECSY_ENTITIES> entities_bitset;
+        entity_id entity_counter = 0;
+    };
+
+    inline entity_id world::make_entity()
+    {
+        auto id = entity_counter;
+        entities_bitset.set(id);
+    
+        entity_counter++;
+    
+        return id;
+    }
+
+    inline bool world::is_alive(entity_id e) const
+    {
+        return entities_bitset.test(e);
+    }
+};