diff --git a/src/common_code/common_code.cc b/src/common_code/common_code.cc
index 5db389a..f9d84f8 100644
--- a/src/common_code/common_code.cc
+++ b/src/common_code/common_code.cc
@@ -88,37 +88,7 @@ std::string CommonCode::to_string(bool shorten) const { // convert uint64_t code
     return result; // char* -> std::string
 }
 
-bool CommonCode::check(uint64_t common_code) { // check whether common code is valid
-    uint32_t head = common_code >> 32;
-    if (head >= 16 || (head & 0b11) == 0b11) { // check 2x2 block address
-        return false; // invalid common code
-    }
-
-    /// ensure that there are >= 2 space blocks
-    uint32_t fill_num = 0, space_num = 0;
-    auto range = Common::range_reverse((uint32_t)common_code); // get common code range
-    for (int i = 0; i < 32; i += 2) { // traverse range
-        switch ((range >> i) & 0b11) {
-            case 0b00: // space block
-                ++space_num;
-            case 0b11: // 1x1 block
-                ++fill_num;
-                break;
-            case 0b01: // 1x2 block
-            case 0b10: // 2x1 block
-                fill_num += 2;
-        }
-        if (fill_num >= 16) { // all block filled
-            break;
-        }
-    }
-    if (space_num < 2) {
-        return false; // at least 2 space
-    }
-    return Common::check_case(head, range); // check by head and range
-}
-
-bool CommonCode::check_demo(uint64_t common_code) {
+bool CommonCode::check(uint64_t common_code) { // whether common code is valid
     ///   M_1x1     M_1x2     M_2x1     M_2x2
     ///  1 0 0 0   1 1 0 0   1 0 0 0   1 1 0 0
     ///  0 0 0 0   0 0 0 0   1 0 0 0   1 1 0 0
diff --git a/src/common_code/common_code.h b/src/common_code/common_code.h
index 14006c6..ebb9679 100644
--- a/src/common_code/common_code.h
+++ b/src/common_code/common_code.h
@@ -14,8 +14,6 @@ public:
     static bool check(uint64_t common_code);
     static CommonCode unsafe_create(uint64_t code);
 
-    static bool check_demo(uint64_t common_code);
-
     RawCode to_raw_code() const;
     ShortCode to_short_code() const;
     std::string to_string(bool shorten = false) const;
diff --git a/src/main.cc b/src/main.cc
index 9d1733d..d9dd5a9 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -337,7 +337,7 @@ int main() {
 
 //    int sum = 0;
     for (uint64_t common_code = 0; common_code < 0x1000000000; ++common_code) {
-        if (CommonCode::check_demo(common_code)) {
+        if (CommonCode::check(common_code)) {
             printf("%09lX\n", common_code);
 //            ++sum;
         }
diff --git a/src/utils/common.cc b/src/utils/common.cc
index bd845e3..1886b76 100644
--- a/src/utils/common.cc
+++ b/src/utils/common.cc
@@ -7,38 +7,6 @@ uint32_t Common::range_reverse(uint32_t bin) { // reverse binary every 2-bits
     return ((bin << 2) & 0xCCCCCCCC) | ((bin >> 2) & 0x33333333);
 }
 
-// TODO: remove legacy function -> combine as single function in CommonCode
-bool Common::check_case(uint32_t head, uint32_t range) { // whether the head and range is valid
-    uint32_t mask = 0b110011 << head; // fill 2x2 block
-    for (int addr = 0; range; range >>= 2) { // traverse every 2-bits
-        while (mask >> addr & 0b1) {
-            ++addr; // search next not filled block
-        }
-        switch (range & 0b11) {
-            case 0b00: // space block
-            case 0b11: // 1x1 block
-                if (addr > 19) { // invalid address
-                    return false;
-                }
-                mask |= 0b1 << addr; // fill 1x1 block
-                break;
-            case 0b10: // 2x1 block
-                if (addr > 15 || mask >> (addr + 4) & 0b1) { // invalid address
-                    return false;
-                }
-                mask |= 0b10001 << addr; // fill 2x1 block
-                break;
-            case 0b01: // 1x2 block
-                if (addr > 18 || (addr & 0b11) == 0b11 || mask >> (addr + 1) & 0b1) { // invalid address
-                    return false;
-                }
-                mask |= 0b11 << addr; // fill 1x2 block
-                break;
-        }
-    }
-    return true; // valid case
-}
-
 /// NOTE: don't check unknown ranges
 uint8_t Common::check_range(uint32_t head, uint32_t range) { // check generated range
     ///   M_1x1     M_1x2     M_2x1     M_2x2
diff --git a/src/utils/common.h b/src/utils/common.h
index 2f2c4dc..da713c2 100644
--- a/src/utils/common.h
+++ b/src/utils/common.h
@@ -42,7 +42,7 @@
 class Common {
 public:
     static uint32_t range_reverse(uint32_t bin);
-    static bool check_case(uint32_t head, uint32_t range);
+//    static bool check_case(uint32_t head, uint32_t range);
 
     // TODO: with broken block offset return
     static uint8_t check_range(uint32_t head, uint32_t range);