diff --git a/README.md b/README.md
index 2dda15b..3e68418 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@ See `File -> Preferences -> Settings -> Extensions -> Texinfo` for details. The
 
 * If syntax highlighting is not satisfactory, try another color theme where keyword/operator colors are distinct (e.g. Solarized Light/Dark, Monokai).
 * Preview content is updated on document save rather than document change.
-* For macOS users: Version of preinstalled GNU Texinfo is very old, use a latest one instead. This can be easily done by `brew install texinfo` and change extension setting `texinfo.makeinfo` value.
+* For macOS users: Preinstalled GNU Texinfo distribution is very old. Use a latest one instead. This can be easily done by `brew install texinfo` and change extension setting `texinfo.makeinfo` value.
 
 ## Future Plans
 
diff --git a/language-config.json b/language-config.json
new file mode 100644
index 0000000..7e34c3b
--- /dev/null
+++ b/language-config.json
@@ -0,0 +1,22 @@
+{
+    "comments": {
+        "lineComment": "@c"
+    },
+    "brackets": [
+        ["{", "}"],
+        ["[", "]"],
+        ["(", ")"],
+        ["``", "''"]
+    ],
+    "autoClosingPairs": [
+        ["{", "}"],
+        ["[", "]"],
+        ["(", ")"]
+    ],
+    "surroundingPairs": [
+        ["{", "}"],
+        ["[", "]"],
+        ["(", ")"],
+        ["`", "'"]
+    ]
+}
diff --git a/language-configuration.json b/language-configuration.json
deleted file mode 100644
index 568b405..0000000
--- a/language-configuration.json
+++ /dev/null
@@ -1,14 +0,0 @@
-{
-    "comments": {
-        "lineComment": "@c"
-    },
-    "brackets": [
-        ["{", "}"]
-    ],
-    "autoClosingPairs": [
-        ["{", "}"]
-    ],
-    "surroundingPairs": [
-        ["{", "}"]
-    ]
-}
diff --git a/package.json b/package.json
index 7cdd430..3e8a791 100644
--- a/package.json
+++ b/package.json
@@ -160,15 +160,14 @@
                     ".texinfo",
                     ".txi"
                 ],
-                "configuration": "./language-configuration.json"
+                "configuration": "./language-config.json"
             }
         ],
         "grammars": [
             {
                 "language": "texinfo",
                 "scopeName": "text.texinfo",
-                "path": "./out/texinfo.tmGrammar.json",
-                "configuration": "./language-configuration.json"
+                "path": "./out/grammars/texinfo.json"
             }
         ]
     }
diff --git a/scripts/prepare.sh b/scripts/prepare.sh
index 58f8f2f..4c3c2aa 100755
--- a/scripts/prepare.sh
+++ b/scripts/prepare.sh
@@ -1,8 +1,8 @@
 #!/usr/bin/env sh
 
-mkdir -p ./out
+mkdir -p ./out/grammars
 
 # Convert TextMate grammar from CSON to JSON (VSCode cannot recognize CSON ones).
 TMGRAMMAR_CSON=./node_modules/language-texinfo/grammars/texinfo.cson
-TMGRAMMAR_JSON=./out/texinfo.tmGrammar.json
+TMGRAMMAR_JSON=./out/grammars/texinfo.json
 cson2json $TMGRAMMAR_CSON > $TMGRAMMAR_JSON
diff --git a/src/folding.ts b/src/folding.ts
index 981b7a5..0a5af57 100644
--- a/src/folding.ts
+++ b/src/folding.ts
@@ -84,7 +84,7 @@ export class FoldingRangeContext {
 
     private bufferedFoldingRanges?: vscode.FoldingRange[];
 
-    private commentRange?: [number, number];
+    private commentRange?: { start: number, end: number };
 
     private headerStart?: number;
 
@@ -99,7 +99,6 @@ export class FoldingRangeContext {
      * @param end Ending line number.
      */
     private calculateFoldingRanges() {
-        this.commentRange = undefined;
         this.headerStart = undefined;
         const closingBlocks = <{ name: string, line: number }[]>[];
         for (let idx = this.document.lineCount - 1; idx >= 0; --idx) {
@@ -116,7 +115,7 @@ export class FoldingRangeContext {
             } else {
                 const closingBlock = closingBlocks.pop();
                 if (closingBlock === undefined) {
-                    return;
+                    continue;
                 }
                 if (line.substring(1, closingBlock.name.length + 2).trim() === closingBlock.name) {
                     this.insertRange(idx, closingBlock.line);
@@ -126,9 +125,9 @@ export class FoldingRangeContext {
             }
         }
         if (this.commentRange !== undefined) {
-            this.insertRange(this.commentRange[0], this.commentRange[1], vscode.FoldingRangeKind.Comment);
+            this.insertRange(this.commentRange.start, this.commentRange.end, vscode.FoldingRangeKind.Comment);
         }
-        return this.bufferedFoldingRanges;
+        this.commentRange = undefined;
     }
 
     private processComment(lineText: string, lineNum: number) {
@@ -147,12 +146,12 @@ export class FoldingRangeContext {
                 return true;
             }
             if (this.commentRange === undefined) {
-                this.commentRange = [lineNum, lineNum];
-            } else if (this.commentRange[0] - 1 === lineNum) {
-                this.commentRange[0] = lineNum;
+                this.commentRange = { start: lineNum, end: lineNum };
+            } else if (this.commentRange.start - 1 === lineNum) {
+                this.commentRange.start = lineNum;
             } else {
-                this.insertRange(this.commentRange[0], this.commentRange[1], vscode.FoldingRangeKind.Comment);
-                this.commentRange = [lineNum, lineNum];
+                this.insertRange(this.commentRange.start, this.commentRange.end, vscode.FoldingRangeKind.Comment);
+                this.commentRange = { start: lineNum, end: lineNum };
             }
             return true;
         }
diff --git a/src/options.ts b/src/options.ts
index 8bb93e2..8a0e6ec 100644
--- a/src/options.ts
+++ b/src/options.ts
@@ -7,8 +7,6 @@
 
 import * as vscode from 'vscode';
 
-let options: Options | undefined;
-
 /**
  * Fetch extension option values.
  * 
@@ -16,12 +14,14 @@ let options: Options | undefined;
  */
 export default class Options {
 
+    private static singleton?: Options;
+
     private static get instance() {
-        return options ?? (options = new Options('texinfo'));
+        return Options.singleton ?? (Options.singleton = new Options('texinfo'));
     }
 
     static clear() {
-        options = undefined;
+        Options.singleton = undefined;
     }
 
     static get makeinfo() {
diff --git a/src/preview.ts b/src/preview.ts
index c2ef413..7287cd5 100644
--- a/src/preview.ts
+++ b/src/preview.ts
@@ -126,8 +126,6 @@ export default class Preview {
         this.updating = false;
         this.updateTitle();
 
-        if (this.pendingUpdate) {
-            this.updateWebview();
-        }
+        this.pendingUpdate && this.updateWebview();
     }
 }