diff --git a/src/klotski_core/core/core.h b/src/klotski_core/core/core.h
index 4b770c6..e9529d0 100644
--- a/src/klotski_core/core/core.h
+++ b/src/klotski_core/core/core.h
@@ -1,5 +1,31 @@
 #pragma once
 
+/// The main purpose of klotski calculation is to obtain all the next steps in order to carry
+/// out the BFS algorithm. The definition of the next step is the result of moving an arbitrary
+/// block in the current layout for a limited number of times, and the resulting layout is
+/// different from the original.
+
+///   Eg1:
+///     % # # %       % # # %    % # # %    % # # %    % # # %    % # # %    % # # %    % # # %    % # # %
+///     % # # %       % # # %    % # # %    % # # %    % # # %    % # # %    % # # %    % # # %    % # # %
+///     @ $ $ @  ==>  @ $ $ @    @ $ $ @    @ $ $ @    @ $ $ @    @ $ $ @    @ $ $ @    @ $ $ @    @ $ $ @
+///     @ & * @       @   * @    @   * @    @ &   @    @ &   @    @ & * @    @ & * @    @ & * @    @ & * @
+///     *     &       * &   &    *   & &    *   * &    * *   &      *   &        * &    *   &      * &
+
+///   Eg2:
+///     * @ & %       * @ & %    * @ & %    * @ & %
+///     # # $ %       # # $ %    # # $ %    # # $ %
+///     # # $ ^  ==>  # # $ ^    # # $ ^    # # $ ^
+///       ~ ~ ^       ~ ~   ^      ~ ~ ^    @ ~ ~ ^
+///       @ % %         @ % %    @   % %        % %
+
+/// In order to achieve the purpose of searching for the next step, we should find out the
+/// sub-layout that can be derived from each block. Due to the limited steps of moving, with
+/// the help of a sub-BFS search, the target can be obtained. It can be shown that this step
+/// produces at most 15 derived layouts, so it can be stored and computed in a queue of length
+/// 16. By performing such a search on each block in the layout, we can get all the next-step
+/// layouts, which have a minimum of 0 and a maximum of 68.
+
 #include <cstdint>
 #include <utility>
 #include <functional>
diff --git a/src/klotski_core/ffi/tmain.cc b/src/klotski_core/ffi/tmain.cc
index a6848b7..34e1b6d 100644
--- a/src/klotski_core/ffi/tmain.cc
+++ b/src/klotski_core/ffi/tmain.cc
@@ -1,30 +1,76 @@
 #include <cstdio>
-
-//#include <iostream>
+#include <iostream>
+#include <algorithm>
 
 #include "klotski.h"
-//#include "core.h"
+#include "core.h"
 
 //#include "common.h"
 #include "benchmark.h"
 
 #include "all_cases.h"
+#include "common_code.h"
 
 using namespace klotski;
 
 void tmain() {
     printf("tmain start\n");
 
-    printf("%d\n", ALL_CASES_SIZE_SUM);
+//    printf("%d\n", ALL_CASES_SIZE_SUM);
 //    std::cout << ALL_CASES_SIZE_SUM << std::endl;
 
 //    uint64_t common_code = 0x1A9BC0C00;
 //    klotski::Common::range_reverse(common_code);
 
-    printf("%f\n", Benchmark::basic_ranges(Benchmark::MS));
-    printf("%f\n", Benchmark::all_cases(Benchmark::MS));
+//    printf("%f\n", Benchmark::basic_ranges(Benchmark::MS));
+//    printf("%f\n", Benchmark::all_cases(Benchmark::MS));
 //    std::cout << Benchmark::basic_ranges(Benchmark::MS) << std::endl;
 //    std::cout << Benchmark::all_cases(Benchmark::MS) << std::endl;
 
+
+    std::vector<uint64_t> next;
+
+    auto core = Core([&next](uint64_t code, uint64_t) {
+        next.emplace_back(code);
+    });
+
+    auto next_num = [&core, &next](uint64_t raw_code) -> uint32_t {
+        next.clear();
+        core.next_cases(raw_code, 0);
+        return next.size();
+    };
+
+    std::vector<uint64_t> all_cases;
+
+    for (uint64_t head = 0; head < 16; ++head) {
+
+        for (const auto &range : AllCases::fetch()[head]) {
+
+            uint64_t raw_code = RawCode::from_common_code(head << 32 | range).unwrap();
+
+            all_cases.emplace_back(raw_code);
+
+        }
+
+    }
+
+    std::vector<uint32_t> next_size;
+
+    std::cout << "start search" << std::endl;
+
+    auto start = clock();
+
+    for (const auto &c : all_cases) {
+
+        next_size.emplace_back(next_num(c));
+
+    }
+
+    std::cout << ((clock() - start) * 1000 / CLOCKS_PER_SEC) << "ms" << std::endl;
+
+    std::sort(next_size.begin(), next_size.end());
+    std::cout << next_size[0] << std::endl;
+    std::cout << next_size[next_size.size() - 1] << std::endl;
+
     printf("tmain exit\n");
 }
diff --git a/src/main.c b/src/main.c
index 2fdcb46..3d27c09 100644
--- a/src/main.c
+++ b/src/main.c
@@ -4,7 +4,7 @@
 int main() {
 //    printf("cli boot\n");
 
-//    tmain();
+    tmain();
     return 0;
 
 //    bool ret = common_code_check(0x1A9BF0C00);