diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index 73d7925..fc79b46 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -2,7 +2,8 @@
 
 $finder = PhpCsFixer\Finder::create()
     ->exclude([
-        'tests/data'
+        'tests/data',
+        'playground',
     ])
     ->in(__DIR__);
 
diff --git a/README.md b/README.md
index 0f3669f..09d76c4 100644
--- a/README.md
+++ b/README.md
@@ -64,16 +64,38 @@ You can customize in your `phpstan.neon`:
 ```neon
 parameters:
     friendly:
-        # default is 3
-        lineBefore: 3
-        lineAfter: 3
-        # default is null
+        lineBefore: 3  # Number of lines to display before error line (default: 2)
+        lineAfter: 3   # Number of lines to display after error line (default: 2)
+        editorUrl: 'phpstorm://open?file=%%file%%&line=%%line%%'  # Editor URL (default: null)
+```
+
+### Editor URL Configuration
+
+The `editorUrl` option allows you to create clickable links in terminal output that open files directly in your editor.
+
+**Available placeholders:**
+- `%%file%%` - Absolute file path
+- `%%relFile%%` - Relative file path (useful for Docker/container environments)
+- `%%line%%` - Line number
+
+**Editor examples:**
+```neon
+parameters:
+    friendly:
+        # PhpStorm / IntelliJ IDEA
         editorUrl: 'phpstorm://open?file=%%file%%&line=%%line%%'
+
+        # VSCode (with absolute path)
+        editorUrl: 'vscode://file/%%file%%:%%line%%'
+
+        # VSCode (with relative path - for Docker environments, requires base path)
+        editorUrl: 'vscode://file//your/local/project/path/%%relFile%%:%%line%%'
+
+        # Sublime Text
+        editorUrl: 'subl://open?url=file://%%file%%&line=%%line%%'
 ```
 
-- `lineBefore` ... Number of lines to display before error line
-- `lineAfter` ... Number of lines to display after error line
-- `editorUrl` ... URL with placeholders like [table formatter config](URL for editor like table formatter)
+> **Note:** When running PHPStan in Docker or other virtualized environments, use `%%relFile%%` instead of `%%file%%` to get the relative path. For VSCode, you may need to prepend your local project path since VSCode requires absolute paths.
 
 
 ## 🖼️ Example
diff --git a/composer.json b/composer.json
index 68d617d..2a98806 100644
--- a/composer.json
+++ b/composer.json
@@ -51,6 +51,7 @@
         "analyze": "phpstan analyze -c phpstan.neon.dist --error-format friendly",
         "analyze-raw": "phpstan analyze -c phpstan.neon.dist --error-format raw",
         "analyze-table": "phpstan analyze -c phpstan.neon.dist --error-format table",
+        "playground": "phpstan analyze playground -c playground/phpstan.neon --error-format friendly",
         "cs-fix": "php-cs-fixer fix",
         "cs-fix-dry": "php-cs-fixer fix --dry-run"
     }
diff --git a/phpstan.neon.dist b/phpstan.neon.dist
index 10339bd..8d4907b 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon.dist
@@ -38,3 +38,7 @@ parameters:
     friendly:
         lineBefore: 2
         lineAfter: 2
+        # editorUrl examples:
+        # - PhpStorm: 'phpstorm://open?file=%%relFile%%&line=%%line%%'
+        # - VSCode (local): 'vscode://file//path/to/project/%%relFile%%:%%line%%'
+        editorUrl: null
diff --git a/playground/dead_code.php b/playground/dead_code.php
new file mode 100644
index 0000000..23cbb9c
--- /dev/null
+++ b/playground/dead_code.php
@@ -0,0 +1,52 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Dead code and unreachable code errors for PHPStan testing
+ */
+
+// 1. Unreachable code after return
+function unreachableAfterReturn(): string
+{
+    return 'hello';
+    echo 'This is unreachable'; // Error: unreachable
+}
+
+// 2. Unreachable code after throw
+function unreachableAfterThrow(): void
+{
+    throw new RuntimeException('Error');
+    echo 'Never executed'; // Error: unreachable
+}
+
+// 3. Always true/false condition
+function alwaysTrueCondition(): void
+{
+    $value = 'string';
+    if (is_string($value)) { // Error: always true
+        echo 'Always executes';
+    }
+}
+
+// 4. Impossible type check
+function impossibleCheck(int $value): void
+{
+    if (is_string($value)) { // Error: impossible, $value is int
+        echo 'Never happens';
+    }
+}
+
+// 5. Unused private method
+class ClassWithDeadCode
+{
+    public function publicMethod(): void
+    {
+        echo 'public';
+    }
+
+    private function unusedPrivateMethod(): void // Error: unused
+    {
+        echo 'never called';
+    }
+}
diff --git a/playground/logic_errors.php b/playground/logic_errors.php
new file mode 100644
index 0000000..fb0c56e
--- /dev/null
+++ b/playground/logic_errors.php
@@ -0,0 +1,58 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Logic and comparison errors for PHPStan testing
+ */
+
+// 1. Strict comparison with different types
+function strictComparison(): bool
+{
+    return 'string' === 123; // Error: comparing different types
+}
+
+// 2. Division by zero
+function divisionByZero(): float
+{
+    $divisor = 0;
+    return 100 / $divisor; // Error: division by zero
+}
+
+// 3. Array access on non-array
+function arrayAccessOnString(): string
+{
+    $value = 'hello';
+    return $value['key']; // Error: invalid array access
+}
+
+// 4. Instanceof with final class that doesn't match
+final class FinalClass
+{
+}
+
+class OtherClass
+{
+}
+
+function impossibleInstanceof(OtherClass $obj): bool
+{
+    return $obj instanceof FinalClass; // Error: impossible
+}
+
+// 5. Wrong number of arguments
+function expectsThreeArgs(int $a, int $b, int $c): int
+{
+    return $a + $b + $c;
+}
+
+$result = expectsThreeArgs(1, 2); // Error: missing argument
+
+// 6. Duplicate array key
+function duplicateKeys(): array
+{
+    return [
+        'key' => 'first',
+        'key' => 'second', // Error: duplicate key
+    ];
+}
diff --git a/playground/missing_types.php b/playground/missing_types.php
new file mode 100644
index 0000000..8b65ba8
--- /dev/null
+++ b/playground/missing_types.php
@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Missing type declarations for PHPStan testing
+ */
+
+// 1. Missing return type
+function noReturnType() // Error at higher levels: missing return type
+{
+    return 'hello';
+}
+
+// 2. Missing parameter type
+function noParamType($value): string // Error at higher levels: missing param type
+{
+    return (string) $value;
+}
+
+// 3. Missing property type
+class MissingTypes
+{
+    public $untyped; // Error at higher levels: missing property type
+
+    private $alsoUntyped = 'default'; // Error at higher levels
+
+    public function process($input) // Error: missing types
+    {
+        $this->untyped = $input;
+        return $input;
+    }
+}
+
+// 4. Mixed type usage
+function usesMixed(mixed $value): mixed
+{
+    return $value->someMethod(); // Error: calling method on mixed
+}
diff --git a/playground/phpstan.neon b/playground/phpstan.neon
new file mode 100644
index 0000000..36aa70d
--- /dev/null
+++ b/playground/phpstan.neon
@@ -0,0 +1,16 @@
+# PHPStan configuration for playground
+# Usage: cd playground && ../vendor/bin/phpstan analyze
+
+includes:
+    - ../extension.neon
+
+parameters:
+    level: 9
+    paths:
+        - .
+
+    # Friendly formatter settings
+    friendly:
+        lineBefore: 3
+        lineAfter: 3
+        editorUrl: 'vscode://file/%%relFile%%:%%line%%'
diff --git a/playground/type_errors.php b/playground/type_errors.php
new file mode 100644
index 0000000..5d4698d
--- /dev/null
+++ b/playground/type_errors.php
@@ -0,0 +1,56 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Type-related errors for PHPStan testing
+ */
+
+// 1. Wrong return type
+function getString(): string
+{
+    return 123; // Error: should return string
+}
+
+// 2. Wrong argument type
+function expectsInt(int $value): void
+{
+    echo $value;
+}
+
+expectsInt('not an int'); // Error: wrong argument type
+
+// 3. Nullable type not handled
+function processString(string $value): int
+{
+    return strlen($value);
+}
+
+function mayReturnNull(): ?string
+{
+    return rand(0, 1) ? 'hello' : null;
+}
+
+processString(mayReturnNull()); // Error: might be null
+
+// 4. Array type mismatch
+/** @param array<int, string> $items */
+function processStringArray(array $items): void
+{
+    foreach ($items as $item) {
+        echo $item;
+    }
+}
+
+processStringArray([1, 2, 3]); // Error: array of int, not string
+
+// 5. Property type mismatch
+class TypedClass
+{
+    public string $name;
+
+    public function __construct()
+    {
+        $this->name = 42; // Error: wrong type
+    }
+}
diff --git a/playground/undefined_errors.php b/playground/undefined_errors.php
new file mode 100644
index 0000000..2e9d2ec
--- /dev/null
+++ b/playground/undefined_errors.php
@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Undefined variable/method/class errors for PHPStan testing
+ */
+
+// 1. Undefined variable
+function useUndefinedVar(): void
+{
+    echo $undefinedVariable; // Error: undefined variable
+}
+
+// 2. Undefined method
+class SomeClass
+{
+    public function existingMethod(): void
+    {
+    }
+}
+
+$obj = new SomeClass();
+$obj->nonExistentMethod(); // Error: undefined method
+
+// 3. Undefined class
+$instance = new NonExistentClass(); // Error: undefined class
+
+// 4. Undefined constant
+echo UNDEFINED_CONSTANT; // Error: undefined constant
+
+// 5. Undefined property
+class AnotherClass
+{
+    public string $definedProperty = 'hello';
+}
+
+$another = new AnotherClass();
+echo $another->undefinedProperty; // Error: undefined property
+
+// 6. Undefined function
+undefinedFunction(); // Error: undefined function