diff --git a/README.md b/README.md
index 0007380..9bff5a1 100644
--- a/README.md
+++ b/README.md
@@ -21,4 +21,12 @@ Add to user environment variables
 
 ```
 Lua51_ROOT = "C:\<path_to_cpp-skill>\windows\lua"
+```
+
+
+## Build
+
+```
+cmake -DCMAKE_BUILD_TYPE=Release -S . -B build
+cmake --build build --target all
 ```
\ No newline at end of file
diff --git a/basics/constness/CMakeLists.txt b/basics/constness/CMakeLists.txt
index 04e4154..1e2645a 100644
--- a/basics/constness/CMakeLists.txt
+++ b/basics/constness/CMakeLists.txt
@@ -1,2 +1,5 @@
 add_executable(const-1 const-1.cpp)
 add_executable(const-2 const-2.cpp)
+add_executable(const-3 const-3.cpp)
+add_executable(const-4 const-4.cpp)
+add_executable(const-5 const-5.cpp)
diff --git a/basics/constness/const-1.cpp b/basics/constness/const-1.cpp
index 85acd13..cf4e121 100644
--- a/basics/constness/const-1.cpp
+++ b/basics/constness/const-1.cpp
@@ -2,7 +2,7 @@ int main(int argc, char const *argv[])
 {
     const char* const_variable = nullptr;
     const_variable = new char[5];
-    const_variable[0] = 'H'; // error: expression must be a modifiable lvalue
-    delete const_variable;
+    // const_variable[0] = 'H'; // error: expression must be a modifiable lvalue
+    delete[] const_variable;
     return 0;
 }
diff --git a/basics/constness/const-2.cpp b/basics/constness/const-2.cpp
index 6757e65..0354748 100644
--- a/basics/constness/const-2.cpp
+++ b/basics/constness/const-2.cpp
@@ -1,8 +1,8 @@
 int main(int argc, char const *argv[])
 {
     char* const const_variable = nullptr;
-    const_variable = new char[5]; // error: expression must be a modifiable lvalue
+    // const_variable = new char[5]; // error: expression must be a modifiable lvalue
     const_variable[0] = 'H';
-    delete const_variable;
+    delete[] const_variable;
     return 0;
 }
diff --git a/basics/constness/const-3.cpp b/basics/constness/const-3.cpp
index e97fef1..97aebc9 100644
--- a/basics/constness/const-3.cpp
+++ b/basics/constness/const-3.cpp
@@ -7,6 +7,6 @@ int main(int argc, char const *argv[])
     const_variable[3] = 'l';
     const_variable[4] = 'o';
     delete const_variable;
-    const_variable = nullptr; // error: expression must be a modifiable lvalue
+    // cons[]t_variable = nullptr; // error: expression must be a modifiable lvalue
     return 0;
 }
diff --git a/basics/constness/const-4.cpp b/basics/constness/const-4.cpp
index 1bdadf4..8e9fd8f 100644
--- a/basics/constness/const-4.cpp
+++ b/basics/constness/const-4.cpp
@@ -1,8 +1,8 @@
 int main(int argc, char const *argv[])
 {
     const char* const const_variable = new char[5];
-    const_variable[0] = 'H'; // error: expression must be a modifiable lvalue
-    delete const_variable;
-    const_variable = nullptr; // error: expression must be a modifiable lvalue
+    // const_variable[0] = 'H'; // error: expression must be a modifiable lvalue
+    delete[] const_variable;
+    // const_variable = nullptr; // error: expression must be a modifiable lvalue
     return 0;
 }
diff --git a/oop/destructor/protected-destructor.cpp b/oop/destructor/protected-destructor.cpp
index dfb9d07..8148d74 100644
--- a/oop/destructor/protected-destructor.cpp
+++ b/oop/destructor/protected-destructor.cpp
@@ -13,8 +13,8 @@ class ProtectedDestructor {
 
 int main(int argc, char const *argv[])
 {
-    ProtectedDestructor* obj = new ProtectedDestructor();
+    const ProtectedDestructor* obj = new ProtectedDestructor();
     // delete dynamic_cast<PleaseLetMeDelete*>(obj);
-    delete obj;
+    // delete obj; // error: destructor is inaccessible
     return 0;
 }
diff --git a/oop/non_copyable/CMakeLists.txt b/oop/non_copyable/CMakeLists.txt
index a83fe24..549d36a 100644
--- a/oop/non_copyable/CMakeLists.txt
+++ b/oop/non_copyable/CMakeLists.txt
@@ -1,4 +1,3 @@
-# set(CMAKE_CXX_STANDARD 17)
-add_executable(non-copyable non-copyable.cpp)
+# add_executable(non-copyable non-copyable.cpp)
 add_executable(func-in-derived-class func-in-derived-class.cpp)
 add_executable(func-in-derived-2 func-in-derived-2.cpp)
diff --git a/patterns/CMakeLists.txt b/patterns/CMakeLists.txt
index bd7ee6a..8013cd1 100644
--- a/patterns/CMakeLists.txt
+++ b/patterns/CMakeLists.txt
@@ -1,2 +1,2 @@
 add_subdirectory(factory)
-add_subdirectory(fsm)
\ No newline at end of file
+# add_subdirectory(fsm)
\ No newline at end of file
diff --git a/rand/CMakeLists.txt b/rand/CMakeLists.txt
index 8229d0f..bd1f072 100644
--- a/rand/CMakeLists.txt
+++ b/rand/CMakeLists.txt
@@ -2,5 +2,6 @@ set(CMAKE_CXX_STANDARD 20)
 
 add_executable(randomness_test randomness-test.c)
 configure_file(decoded-20240131051421.bin ${CMAKE_CURRENT_BINARY_DIR}/decoded-20240131051421.bin COPYONLY)
+target_link_libraries(randomness_test m)
 
 add_executable(tony_rand lrand.c)
\ No newline at end of file
diff --git a/rand/randomness-test.c b/rand/randomness-test.c
index 3dbbda5..e6c08ae 100644
--- a/rand/randomness-test.c
+++ b/rand/randomness-test.c
@@ -144,12 +144,14 @@ int main(int argc, char const *argv[])
   fseek(f, 0, SEEK_END);
   int size = ftell(f);
   printf("found %d bytes in binary file\n", size);
-  if (size <= 0)
+  if (size <= 0) {
+    fclose(f);
     return -1;
+  }
   
   fseek(f, 0, SEEK_SET);
 
-  int8_t *values = malloc(size);
+  int8_t* values = (int8_t*)malloc(size);
   fread(values, sizeof(int8_t), size, f);
   fclose(f);
 
diff --git a/serialization/save-number.cpp b/serialization/save-number.cpp
index eb6221b..608256c 100644
--- a/serialization/save-number.cpp
+++ b/serialization/save-number.cpp
@@ -1,4 +1,5 @@
 #include <iostream>
+#include <stdint.h>
 
 #define MIN(a, b) ((a < b) ? a : b)
 
diff --git a/serialization/write-number.cpp b/serialization/write-number.cpp
index 0ccadf5..dd2151a 100644
--- a/serialization/write-number.cpp
+++ b/serialization/write-number.cpp
@@ -3,7 +3,8 @@
 #include <limits>
 #include <string>
 
-static char mem[100] 
+static char mem[100];
+
 template<typename T>
 void write_number(T v, uint8_t* b, size_t type_size)
 {
@@ -19,7 +20,6 @@ void save_pulse_value_into_nvram(const std::string &file_name_prefix, int id, T
     size_t size = sizeof(T) + 1;
     uint8_t *data = static_cast<uint8_t*>(std::calloc(size, sizeof(uint8_t)));
     write_number<T>(value, data, size);
-    write_file_async(file_name, size, (unsigned char *)data, true);
     free(data);
 }
 
diff --git a/templates/CMakeLists.txt b/templates/CMakeLists.txt
index 321c022..228335d 100644
--- a/templates/CMakeLists.txt
+++ b/templates/CMakeLists.txt
@@ -2,5 +2,5 @@ add_subdirectory(enable_if)
 add_subdirectory(variadic)
 
 set(CMAKE_CXX_STANDARD 20)
-add_executable(why why.cpp)
+# add_executable(why why.cpp)
 add_executable(good-enum good-enum.cpp)
\ No newline at end of file
diff --git a/templates/variadic/variadic-template.cpp b/templates/variadic/variadic-template.cpp
index ddeaa55..3da25cf 100644
--- a/templates/variadic/variadic-template.cpp
+++ b/templates/variadic/variadic-template.cpp
@@ -23,12 +23,11 @@ void cool_function(Hint hint, Ts... args) {
     }
     case Hint::COOL_THREE:
     {
-        if constexpr ()
-        auto print_cool_three = [](const char* string, size_t size) {
-            std::cout << string;
-        };
         std::cout << "COOL THREE: ";
-        print_cool_three(args...);
+        // auto print_cool_three = [](const char* string, size_t size) {
+        //     std::cout << string;
+        // };
+        // print_cool_three(args...);
         std::cout << std::endl;
         break;
     }