diff --git a/src/core/benchmark/ranges.cc b/src/core/benchmark/ranges.cc
index fe8f276..01bb5f3 100644
--- a/src/core/benchmark/ranges.cc
+++ b/src/core/benchmark/ranges.cc
@@ -5,6 +5,7 @@
 #include "all_cases/all_cases.h"
 
 using klotski::cases::AllCases;
+using klotski::cases::BasicRanges;
 
 static void SpawnRanges(benchmark::State &state) {
     // constexpr auto nums = target_nums();
@@ -23,6 +24,13 @@ static void SpawnRanges(benchmark::State &state) {
 
 }
 
+static void RangesReverse(benchmark::State &state) {
+    auto ranges = BasicRanges::instance().fetch();
+    for (auto _ : state) {
+        ranges.reverse();
+    }
+}
+
 static void RangesUnionExport(benchmark::State &state) {
     auto &all_cases = AllCases::instance().fetch();
     for (auto _ : state) {
@@ -71,6 +79,8 @@ static void RangesAt(benchmark::State &state) {
 
 // BENCHMARK(SpawnRanges)->Unit(benchmark::kMillisecond);
 
+// BENCHMARK(RangesReverse)->Unit(benchmark::kMillisecond);
+
 // BENCHMARK(RangesUnionExport)->Unit(benchmark::kMillisecond);
 
 // BENCHMARK(RangesSize);
diff --git a/src/core/ranges/internal/ranges.cc b/src/core/ranges/internal/ranges.cc
index 6abfab8..16ee782 100644
--- a/src/core/ranges/internal/ranges.cc
+++ b/src/core/ranges/internal/ranges.cc
@@ -1,3 +1,5 @@
+#include <span>
+
 #include "ranges/ranges.h"
 #include "common_code/common_code.h"
 
@@ -5,18 +7,10 @@ using klotski::cases::Ranges;
 using klotski::codec::CommonCode;
 using klotski::cases::RangesUnion;
 
-RangesUnion& RangesUnion::operator+=(const RangesUnion &ranges_union) {
-    for (const auto head : Heads) {
-        ranges(head) += ranges_union.ranges(head);
-    }
-    return *this;
-}
-
 std::vector<CommonCode> RangesUnion::codes() const {
     std::vector<CommonCode> codes;
     codes.reserve(size());
     for (const auto head : Heads) {
-        // for (const auto range : (*this)[head]) {
         for (const auto range : ranges(head)) {
             codes.emplace_back(CommonCode::unsafe_create(head << 32 | range));
         }
@@ -26,26 +20,19 @@ std::vector<CommonCode> RangesUnion::codes() const {
 }
 
 KLSK_INLINE CommonCode RangesUnion::operator[](size_type n) const {
-    // uint64_t head = 0;
-    // while (n >= ranges(head).size()) {
-    //     n -= ranges(head).size();
-    //     ++head;
-    // }
-    // KLSK_ASSUME(head < 16);
-    // return CommonCode::unsafe_create(head << 32 | ranges(head)[n]);
-
     if (n < ranges(0).size()) {
         return CommonCode::unsafe_create(ranges(0)[n]);
     }
     n -= ranges(0).size();
 
-    KLSK_UNROLL(sizeof(Heads) - 2)
-    for (const uint64_t head : std::to_array({0x1, 0x2, 0x4, 0x5, 0x6, 0x8, 0x9, 0xA, 0xC, 0xD})) {
+    KLSK_UNROLL(Heads.size() - 2)
+    for (const uint64_t head : std::span {Heads.data() + 1, Heads.size() - 2}) {
         if (n < ranges(head).size()) {
             return CommonCode::unsafe_create(head << 32 | ranges(head)[n]);
         }
         n -= ranges(head).size();
     }
 
-    return CommonCode::unsafe_create((uint64_t)0xE << 32 | ranges(0xE)[n]);
+    constexpr auto head = static_cast<uint64_t>(0xE);
+    return CommonCode::unsafe_create(head << 32 | ranges(0xE)[n]);
 }
diff --git a/src/core/ranges/internal/ranges.inl b/src/core/ranges/internal/ranges.inl
index 73f5304..8aafb86 100644
--- a/src/core/ranges/internal/ranges.inl
+++ b/src/core/ranges/internal/ranges.inl
@@ -3,14 +3,39 @@
 namespace klotski::cases {
 
 KLSK_INLINE_H void Ranges::reverse() {
+    #pragma clang loop vectorize(enable)
     for (auto &x : *this) {
         x = range_reverse(x);
     }
 }
 
+inline Ranges& RangesUnion::ranges(const size_t head) {
+    return std::array<Ranges, 16>::operator[](head);
+}
+
+inline const Ranges& RangesUnion::ranges(const size_t head) const {
+    return std::array<Ranges, 16>::operator[](head);
+}
+
 inline Ranges& Ranges::operator+=(const Ranges &ranges) {
     this->insert(this->end(), ranges.begin(), ranges.end());
     return *this;
 }
 
+inline RangesUnion& RangesUnion::operator+=(const RangesUnion &ranges_union) {
+    for (const auto head : Heads) {
+        ranges(head) += ranges_union.ranges(head);
+    }
+    return *this;
+}
+
+KLSK_INLINE_H size_t RangesUnion::size() const {
+    size_type size = 0;
+    KLSK_UNROLL(sizeof(Heads))
+    for (const auto head : Heads) {
+        size += ranges(head).size();
+    }
+    return size;
+}
+
 } // namespace klotski::cases
diff --git a/src/core/ranges/internal/ranges_union.inl b/src/core/ranges/internal/ranges_union.inl
deleted file mode 100644
index 9e24961..0000000
--- a/src/core/ranges/internal/ranges_union.inl
+++ /dev/null
@@ -1,35 +0,0 @@
-#pragma once
-
-namespace klotski::cases {
-
-inline Ranges& RangesUnion::ranges(const size_t head) {
-    return std::array<Ranges, 16>::operator[](head);
-}
-
-inline const Ranges& RangesUnion::ranges(const size_t head) const {
-    return std::array<Ranges, 16>::operator[](head);
-}
-
-KLSK_INLINE_H size_t RangesUnion::size() const {
-    size_type size = 0;
-    KLSK_UNROLL(sizeof(Heads))
-    for (const auto head : Heads) {
-        size += ranges(head).size();
-    }
-    return size;
-}
-
-// KLSK_INLINE_H uint32_t RangesUnion::operator[](size_type n) const {
-//     size_t head = 0;
-//     for (;;) {
-//         if (n >= ranges(head).size()) {
-//             n -= ranges(head).size();
-//             ++head;
-//         } else {
-//             break;
-//         }
-//     }
-//     return ranges(head)[n];
-// }
-
-} // namespace klotski::cases
diff --git a/src/core/ranges/ranges.h b/src/core/ranges/ranges.h
index 344283b..a4df2b8 100644
--- a/src/core/ranges/ranges.h
+++ b/src/core/ranges/ranges.h
@@ -73,4 +73,3 @@ private:
 } // namespace klotski::cases
 
 #include "internal/ranges.inl"
-#include "internal/ranges_union.inl"