diff --git a/README.md b/README.md
index 581f8ed4..bfeff7d6 100644
--- a/README.md
+++ b/README.md
@@ -181,13 +181,13 @@ $result = $diff->render($renderer);
     [
         {
             "tag": "rep",
-            "base": {
+            "old": {
                 "offset": 0,
                 "lines": [
                     "&lt;<del>p&gt;Hello World!&lt;/p</del>&gt;"
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 0,
                 "lines": [
                     "&lt;<ins>div&gt;Hello World!&lt;/div</ins>&gt;"
@@ -196,13 +196,13 @@ $result = $diff->render($renderer);
         },
         {
             "tag": "eq",
-            "base": {
+            "old": {
                 "offset": 1,
                 "lines": [
                     "~~~~~~~~~~~~~~~~~~~"
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 1,
                 "lines": [
                     "~~~~~~~~~~~~~~~~~~~"
@@ -211,11 +211,11 @@ $result = $diff->render($renderer);
         },
         {
             "tag": "ins",
-            "base": {
+            "old": {
                 "offset": 2,
                 "lines": []
             },
-            "changed": {
+            "new": {
                 "offset": 2,
                 "lines": [
                     "Let's add a new line here."
@@ -224,13 +224,13 @@ $result = $diff->render($renderer);
         },
         {
             "tag": "eq",
-            "base": {
+            "old": {
                 "offset": 2,
                 "lines": [
                     "X"
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 3,
                 "lines": [
                     "X"
@@ -241,13 +241,13 @@ $result = $diff->render($renderer);
     [
         {
             "tag": "eq",
-            "base": {
+            "old": {
                 "offset": 6,
                 "lines": [
                     "N"
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 7,
                 "lines": [
                     "N"
@@ -256,13 +256,13 @@ $result = $diff->render($renderer);
         },
         {
             "tag": "rep",
-            "base": {
+            "old": {
                 "offset": 7,
                 "lines": [
                     "Do you know in <del>Chinese, \"金槍魚罐頭\" means tuna</del> can."
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 8,
                 "lines": [
                     "Do you know in <ins>Japanese, \"魚の缶詰\" means fish</ins> can."
@@ -271,14 +271,14 @@ $result = $diff->render($renderer);
         },
         {
             "tag": "eq",
-            "base": {
+            "old": {
                 "offset": 8,
                 "lines": [
                     "This is just a useless line.",
                     "G"
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 9,
                 "lines": [
                     "This is just a useless line.",
@@ -288,26 +288,26 @@ $result = $diff->render($renderer);
         },
         {
             "tag": "del",
-            "base": {
+            "old": {
                 "offset": 10,
                 "lines": [
                     "// @todo Remember to delete this line"
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 11,
                 "lines": []
             }
         },
         {
             "tag": "eq",
-            "base": {
+            "old": {
                 "offset": 11,
                 "lines": [
                     "Say hello to my neighbors."
                 ]
             },
-            "changed": {
+            "new": {
                 "offset": 11,
                 "lines": [
                     "Say hello to my neighbors."
diff --git a/src/Renderer/Html/AbstractHtml.php b/src/Renderer/Html/AbstractHtml.php
index 78137c72..a71c6e9c 100644
--- a/src/Renderer/Html/AbstractHtml.php
+++ b/src/Renderer/Html/AbstractHtml.php
@@ -80,8 +80,8 @@ public function getChanges(): array
                     if (!empty($lines = \array_slice($old, $i1, ($i2 - $i1)))) {
                         $formattedLines = $this->formatLines($lines);
 
-                        $blocks[$lastBlock]['base']['lines'] += $formattedLines;
-                        $blocks[$lastBlock]['changed']['lines'] += $formattedLines;
+                        $blocks[$lastBlock]['old']['lines'] += $formattedLines;
+                        $blocks[$lastBlock]['new']['lines'] += $formattedLines;
                     }
 
                     continue;
@@ -109,7 +109,7 @@ public function getChanges(): array
                         $lines
                     );
 
-                    $blocks[$lastBlock]['base']['lines'] += $lines;
+                    $blocks[$lastBlock]['old']['lines'] += $lines;
                 }
 
                 if (
@@ -124,7 +124,7 @@ public function getChanges(): array
                         $lines
                     );
 
-                    $blocks[$lastBlock]['changed']['lines'] += $lines;
+                    $blocks[$lastBlock]['new']['lines'] += $lines;
                 }
             }
 
@@ -167,8 +167,8 @@ protected function renderChangedExtent(AbstractLineRenderer $lineRenderer, strin
      * Get the default block.
      *
      * @param string $tag the operation tag
-     * @param int    $i1  begin index of the diff of the source
-     * @param int    $j1  begin index of the diff of the destination
+     * @param int    $i1  begin index of the diff of the old array
+     * @param int    $j1  begin index of the diff of the new array
      *
      * @return array the default block
      */
@@ -176,11 +176,11 @@ protected function getDefaultBlock(string $tag, int $i1, int $j1): array
     {
         return [
             'tag' => $tag,
-            'base' => [
+            'old' => [
                 'offset' => $i1,
                 'lines' => [],
             ],
-            'changed' => [
+            'new' => [
                 'offset' => $j1,
                 'lines' => [],
             ],
diff --git a/src/Renderer/Html/Inline.php b/src/Renderer/Html/Inline.php
index 83f5f4c0..4483cf54 100644
--- a/src/Renderer/Html/Inline.php
+++ b/src/Renderer/Html/Inline.php
@@ -124,14 +124,14 @@ protected function renderTableEqual(array $change): string
     {
         $html = '';
 
-        foreach ($change['base']['lines'] as $no => $line) {
-            $oldLineNum = $change['base']['offset'] + $no + 1;
-            $newLineNum = $change['changed']['offset'] + $no + 1;
+        foreach ($change['old']['lines'] as $no => $line) {
+            $oldLineNum = $change['old']['offset'] + $no + 1;
+            $newLineNum = $change['new']['offset'] + $no + 1;
 
             $html .=
                 '<tr data-type="=">' .
-                    '<th class="f-num">' . $oldLineNum . '</th>' .
-                    '<th class="t-num">' . $newLineNum . '</th>' .
+                    '<th class="n-old">' . $oldLineNum . '</th>' .
+                    '<th class="n-new">' . $newLineNum . '</th>' .
                     '<th class="sign"></th>' .
                     '<td class="old">' . $line . '</td>' .
                 '</tr>';
@@ -151,13 +151,13 @@ protected function renderTableInsert(array $change): string
     {
         $html = '';
 
-        foreach ($change['changed']['lines'] as $no => $newLine) {
-            $newLineNum = $change['changed']['offset'] + $no + 1;
+        foreach ($change['new']['lines'] as $no => $newLine) {
+            $newLineNum = $change['new']['offset'] + $no + 1;
 
             $html .=
                 '<tr data-type="+">' .
                     '<th></th>' .
-                    '<th class="t-num">' . $newLineNum . '</th>' .
+                    '<th class="n-new">' . $newLineNum . '</th>' .
                     '<th class="sign ins">+</th>' .
                     '<td class="new">' . $newLine . '</td>' .
                 '</tr>';
@@ -177,12 +177,12 @@ protected function renderTableDelete(array $change): string
     {
         $html = '';
 
-        foreach ($change['base']['lines'] as $no => $oldLine) {
-            $oldLineNum = $change['base']['offset'] + $no + 1;
+        foreach ($change['old']['lines'] as $no => $oldLine) {
+            $oldLineNum = $change['old']['offset'] + $no + 1;
 
             $html .=
                 '<tr data-type="-">' .
-                    '<th class="f-num">' . $oldLineNum . '</th>' .
+                    '<th class="n-old">' . $oldLineNum . '</th>' .
                     '<th></th>' .
                     '<th class="sign del">-</th>' .
                     '<td class="old">' . $oldLine . '</td>' .
@@ -203,25 +203,25 @@ protected function renderTableReplace(array $change): string
     {
         $html = '';
 
-        foreach ($change['base']['lines'] as $no => $oldLine) {
-            $oldLineNum = $change['base']['offset'] + $no + 1;
+        foreach ($change['old']['lines'] as $no => $oldLine) {
+            $oldLineNum = $change['old']['offset'] + $no + 1;
 
             $html .=
                 '<tr data-type="-">' .
-                    '<th class="f-num">' . $oldLineNum . '</th>' .
+                    '<th class="n-old">' . $oldLineNum . '</th>' .
                     '<th></th>' .
                     '<th class="sign del">-</th>' .
                     '<td class="old">' . $oldLine . '</td>' .
                 '</tr>';
         }
 
-        foreach ($change['changed']['lines'] as $no => $newLine) {
-            $newLineNum = $change['changed']['offset'] + $no + 1;
+        foreach ($change['new']['lines'] as $no => $newLine) {
+            $newLineNum = $change['new']['offset'] + $no + 1;
 
             $html .=
                 '<tr data-type="+">' .
                     '<th></th>' .
-                    '<th class="t-num">' . $newLineNum . '</th>' .
+                    '<th class="n-new">' . $newLineNum . '</th>' .
                     '<th class="sign ins">+</th>' .
                     '<td class="new">' . $newLine . '</td>' .
                 '</tr>';
diff --git a/src/Renderer/Html/SideBySide.php b/src/Renderer/Html/SideBySide.php
index c32b8405..61ea570c 100644
--- a/src/Renderer/Html/SideBySide.php
+++ b/src/Renderer/Html/SideBySide.php
@@ -122,15 +122,15 @@ protected function renderTableEqual(array $change): string
     {
         $html = '';
 
-        foreach ($change['base']['lines'] as $no => $line) {
-            $oldLineNum = $change['base']['offset'] + $no + 1;
-            $newLine = $change['changed']['offset'] + $no + 1;
+        foreach ($change['old']['lines'] as $no => $line) {
+            $oldLineNum = $change['old']['offset'] + $no + 1;
+            $newLine = $change['new']['offset'] + $no + 1;
 
             $html .=
                 '<tr>' .
-                    '<th class="f-num">' . $oldLineNum . '</th>' .
+                    '<th class="n-old">' . $oldLineNum . '</th>' .
                     '<td class="old">' . $line . '</td>' .
-                    '<th class="t-num">' . $newLine . '</th>' .
+                    '<th class="n-new">' . $newLine . '</th>' .
                     '<td class="new">' . $line . '</td>' .
                 '</tr>';
         }
@@ -149,14 +149,14 @@ protected function renderTableInsert(array $change): string
     {
         $html = '';
 
-        foreach ($change['changed']['lines'] as $no => $newLine) {
-            $newLineNum = $change['changed']['offset'] + $no + 1;
+        foreach ($change['new']['lines'] as $no => $newLine) {
+            $newLineNum = $change['new']['offset'] + $no + 1;
 
             $html .=
                 '<tr>' .
                     '<th></th>' .
                     '<td class="old"></td>' .
-                    '<th class="t-num">' . $newLineNum . '</th>' .
+                    '<th class="n-new">' . $newLineNum . '</th>' .
                     '<td class="new">' . $newLine . '</td>' .
                 '</tr>';
         }
@@ -175,12 +175,12 @@ protected function renderTableDelete(array $change): string
     {
         $html = '';
 
-        foreach ($change['base']['lines'] as $no => $oldLine) {
-            $oldLineNum = $change['base']['offset'] + $no + 1;
+        foreach ($change['old']['lines'] as $no => $oldLine) {
+            $oldLineNum = $change['old']['offset'] + $no + 1;
 
             $html .=
                 '<tr>' .
-                    '<th class="f-num">' . $oldLineNum . '</th>' .
+                    '<th class="n-old">' . $oldLineNum . '</th>' .
                     '<td class="old">' . $oldLine . '</td>' .
                     '<th></th>' .
                     '<td class="new"></td>' .
@@ -201,13 +201,13 @@ protected function renderTableReplace(array $change): string
     {
         $html = '';
 
-        if (\count($change['base']['lines']) >= \count($change['changed']['lines'])) {
-            foreach ($change['base']['lines'] as $no => $oldLine) {
-                $oldLineNum = $change['base']['offset'] + $no + 1;
+        if (\count($change['old']['lines']) >= \count($change['new']['lines'])) {
+            foreach ($change['old']['lines'] as $no => $oldLine) {
+                $oldLineNum = $change['old']['offset'] + $no + 1;
 
-                if (isset($change['changed']['lines'][$no])) {
-                    $newLineNum = $change['base']['offset'] + $no + 1;
-                    $newLine = '<span>' . $change['changed']['lines'][$no] . '</span>';
+                if (isset($change['new']['lines'][$no])) {
+                    $newLineNum = $change['old']['offset'] + $no + 1;
+                    $newLine = '<span>' . $change['new']['lines'][$no] . '</span>';
                 } else {
                     $newLineNum = '';
                     $newLine = '';
@@ -215,19 +215,19 @@ protected function renderTableReplace(array $change): string
 
                 $html .=
                     '<tr>' .
-                        '<th class="f-num">' . $oldLineNum . '</th>' .
+                        '<th class="n-old">' . $oldLineNum . '</th>' .
                         '<td class="old"><span>' . $oldLine . '</span></td>' .
-                        '<th class="t-num">' . $newLineNum . '</th>' .
+                        '<th class="n-new">' . $newLineNum . '</th>' .
                         '<td class="new">' . $newLine . '</td>' .
                     '</tr>';
             }
         } else {
-            foreach ($change['changed']['lines'] as $no => $newLine) {
-                $newLineNum = $change['changed']['offset'] + $no + 1;
+            foreach ($change['new']['lines'] as $no => $newLine) {
+                $newLineNum = $change['new']['offset'] + $no + 1;
 
-                if (isset($change['base']['lines'][$no])) {
-                    $oldLineNum = $change['base']['offset'] + $no + 1;
-                    $oldLine = '<span>' . $change['base']['lines'][$no] . '</span>';
+                if (isset($change['old']['lines'][$no])) {
+                    $oldLineNum = $change['old']['offset'] + $no + 1;
+                    $oldLine = '<span>' . $change['old']['lines'][$no] . '</span>';
                 } else {
                     $oldLineNum = '';
                     $oldLine = '';
@@ -235,9 +235,9 @@ protected function renderTableReplace(array $change): string
 
                 $html .=
                     '<tr>' .
-                        '<th class="f-num">' . $oldLineNum . '</th>' .
+                        '<th class="n-old">' . $oldLineNum . '</th>' .
                         '<td class="old"><span>' . $oldLine . '</span></td>' .
-                        '<th class="t-num">' . $newLineNum . '</th>' .
+                        '<th class="n-new">' . $newLineNum . '</th>' .
                         '<td class="new">' . $newLine . '</td>' .
                     '</tr>';
             }