diff --git a/src/core/core.cc b/src/core/core.cc
index 18defa1..df1a6aa 100644
--- a/src/core/core.cc
+++ b/src/core/core.cc
@@ -129,36 +129,33 @@ void Core::move_2x2(uint64_t code, int addr) { // try to move target 2x2 block
 #include <iostream>
 
 void Core::next_step(uint64_t raw_code) {
-
-    auto temp_code = raw_code;
-//    uint64_t raw_code = _code;
-
-    for (int addr = 0; temp_code; addr += 3, temp_code >>= 3) {
-
-        switch (temp_code & 0b111) {
+    auto code = raw_code;
+    for (int addr = 0; code; addr += 3, code >>= 3) { // traverse every 3-bits
+        switch (code & 0b111) { // match low 3-bits
             case B_1x1:
-                move_1x1(raw_code, addr);
+                move_1x1(raw_code, addr); // try to move 1x1 block
                 break;
             case B_1x2:
-                move_1x2(raw_code, addr);
+                move_1x2(raw_code, addr); // try to move 1x2 block
                 break;
             case B_2x1:
-                move_2x1(raw_code, addr);
+                move_2x1(raw_code, addr); // try to move 2x1 block
                 break;
             case B_2x2:
-                move_2x2(raw_code, addr);
+                move_2x2(raw_code, addr); // try to move 2x2 block
                 break;
             default:
                 continue; // B_space or B_fill
         }
-        if (cache_size != 1) {
+        if (cache_size != 1) { // found one or more next cases
             for (int i = 1; i < cache_size; ++i) {
-//                std::cout << RawCode(cache[i].code).dump_case();
-//                printf("(%016lX)\n\n", cache[i].mask);
+
+                // TODO: release next cases (code and mask)
+
+                std::cout << RawCode(cache[i].code).dump_case();
+                printf("(%016lX)\n\n", cache[i].mask);
+
             }
-//            std::cout << "found: " << cache_size - 1 << std::endl;
         }
     }
 }
-
-
diff --git a/src/core/core.h b/src/core/core.h
index a400e69..a94b959 100644
--- a/src/core/core.h
+++ b/src/core/core.h
@@ -19,36 +19,22 @@
 
 class Core {
 public:
+    void next_step(uint64_t raw_code);
+
+private:
     struct cache_t {
-        uint64_t code; // raw code
+        uint64_t code; // case raw code
         uint64_t mask; // only 000 or 111
-        int filter;
-        int addr;
+        int filter; // UP | DOWN | LEFT | RIGHT
+        int addr; // (0 ~ 19) * 3
     };
 
     int cache_size;
     cache_t cache[16];
 
-    inline void cache_insert(Core::cache_t &next_case);
-
     void move_1x1(uint64_t code, int addr);
     void move_1x2(uint64_t code, int addr);
     void move_2x1(uint64_t code, int addr);
     void move_2x2(uint64_t code, int addr);
-
-//    void move_1x1(int addr);
-//    void move_1x2(int addr);
-//    void move_2x1(int addr);
-//    void move_2x2(int addr);
-
-    void next_step(uint64_t raw_code);
-
-//    void next_step();
-
-//    uint64_t _code;
-
-//    Core(uint64_t raw_code) : _code(raw_code) {}
-
+    inline void cache_insert(Core::cache_t &next_case);
 };
-
-
diff --git a/src/main.cc b/src/main.cc
index 812f3c0..3cc5a8a 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -148,9 +148,9 @@ int main() {
 
     auto c = Core();
 //    auto c = Core(raw_code);
-    for (int i = 0; i < 100000000; ++i) {
+//    for (int i = 0; i < 100000000; ++i) {
         c.next_step(raw_code);
-    }
+//    }
 
     return 0;
 }