diff --git a/eslint.config.mjs b/eslint.config.mjs
index a097343..e53eefa 100644
--- a/eslint.config.mjs
+++ b/eslint.config.mjs
@@ -11,9 +11,5 @@ export default antfu(
       },
     },
     typescript: true,
-    rules: {
-      'unused-imports/no-unused-imports': 'error',
-      'unused-imports/no-unused-vars': 'error',
-    }
   },
-);
\ No newline at end of file
+);
diff --git a/package.json b/package.json
index 5c79d11..93346bd 100644
--- a/package.json
+++ b/package.json
@@ -1,15 +1,19 @@
 {
   "name": "questlang-interpreter",
   "version": "1.0.0",
-  "license": "MIT",
   "description": "TypeScript interpreter for QuestLang programming language",
+  "license": "MIT",
   "keywords": [
     "questlang",
     "interpreter",
     "typescript",
     "language"
   ],
-  "type": "module",
+  "exports": {
+    ".": {
+      "import": "./dist/index.js"
+    }
+  },
   "bin": {
     "questlang": "dist/cli.js"
   },
@@ -21,19 +25,14 @@
     "lint": "eslint ./src",
     "lint:fix": "eslint ./src --fix"
   },
+  "dependencies": {
+    "@clack/prompts": "^0.11.0"
+  },
   "devDependencies": {
     "@antfu/eslint-config": "^5.2.1",
     "@robonen/tsconfig": "^0.0.2",
     "tsdown": "^0.14.2",
     "typescript": "^5.9.2",
     "vitest": "^3.2.4"
-  },
-  "dependencies": {
-    "@clack/prompts": "^0.11.0"
-  },
-  "exports": {
-    ".": {
-      "import": "./dist/index.js"
-    }
   }
 }
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index ecddc50..334a237 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -18,6 +18,9 @@ importers:
       '@robonen/tsconfig':
         specifier: ^0.0.2
         version: 0.0.2
+      eslint:
+        specifier: ^9.34.0
+        version: 9.34.0(jiti@2.5.1)
       tsdown:
         specifier: ^0.14.2
         version: 0.14.2(typescript@5.9.2)
diff --git a/src/__tests__/integration.test.ts b/src/__tests__/integration.test.ts
index a701652..d51be36 100644
--- a/src/__tests__/integration.test.ts
+++ b/src/__tests__/integration.test.ts
@@ -138,6 +138,6 @@ describe('questLang Integration', () => {
     interpreter.moveToNode('выбор_пути');
     const choices = interpreter.getAvailableChoices();
     expect(choices).toHaveLength(3);
-    expect(choices[0].text).toBe('Пойти в дешёвую шашлычную');
+    expect(choices[0]?.text).toBe('Пойти в дешёвую шашлычную');
   });
 });
diff --git a/src/__tests__/interpreter.test.ts b/src/__tests__/interpreter.test.ts
index 3177e47..ed89827 100644
--- a/src/__tests__/interpreter.test.ts
+++ b/src/__tests__/interpreter.test.ts
@@ -170,7 +170,7 @@ describe('questInterpreter', () => {
 
     expect(paths.length).toBeGreaterThan(0);
     // Should have at least two paths (налево->победа and направо)
-    expect(paths.some(path => path.includes('победа'))).toBe(true);
-    expect(paths.some(path => path.includes('направо'))).toBe(true);
+    expect(paths.some((path: string) => path.includes('победа'))).toBe(true);
+    expect(paths.some((path: string) => path.includes('направо'))).toBe(true);
   });
 });
diff --git a/src/__tests__/lexer.test.ts b/src/__tests__/lexer.test.ts
index 44c99f4..b2f45d9 100644
--- a/src/__tests__/lexer.test.ts
+++ b/src/__tests__/lexer.test.ts
@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest';
-import { Lexer } from '../lexer';
 import { TokenType } from '..';
+import { Lexer } from '../lexer';
 
 describe('lexer', () => {
   it('should tokenize quest keywords', () => {
@@ -8,19 +8,19 @@ describe('lexer', () => {
     const lexer = new Lexer(source);
     const tokens = lexer.tokenize();
 
-    expect(tokens[0].type).toBe(TokenType.QUEST);
-    expect(tokens[0].value).toBe('квест');
+    expect(tokens[0]?.type).toBe(TokenType.QUEST);
+    expect(tokens[0]?.value).toBe('квест');
 
-    expect(tokens[1].type).toBe(TokenType.IDENTIFIER);
-    expect(tokens[1].value).toBe('Тест');
+    expect(tokens[1]?.type).toBe(TokenType.IDENTIFIER);
+    expect(tokens[1]?.value).toBe('Тест');
 
-    expect(tokens[2].type).toBe(TokenType.SEMICOLON);
+    expect(tokens[2]?.type).toBe(TokenType.SEMICOLON);
 
-    expect(tokens[3].type).toBe(TokenType.GOAL);
-    expect(tokens[3].value).toBe('цель');
+    expect(tokens[3]?.type).toBe(TokenType.GOAL);
+    expect(tokens[3]?.value).toBe('цель');
 
-    expect(tokens[4].type).toBe(TokenType.STRING);
-    expect(tokens[4].value).toBe('Описание');
+    expect(tokens[4]?.type).toBe(TokenType.STRING);
+    expect(tokens[4]?.value).toBe('Описание');
   });
 
   it('should tokenize strings correctly', () => {
@@ -28,8 +28,8 @@ describe('lexer', () => {
     const lexer = new Lexer(source);
     const tokens = lexer.tokenize();
 
-    expect(tokens[0].type).toBe(TokenType.STRING);
-    expect(tokens[0].value).toBe('Тестовая строка с пробелами');
+    expect(tokens[0]?.type).toBe(TokenType.STRING);
+    expect(tokens[0]?.value).toBe('Тестовая строка с пробелами');
   });
 
   it('should tokenize numbers', () => {
@@ -37,11 +37,11 @@ describe('lexer', () => {
     const lexer = new Lexer(source);
     const tokens = lexer.tokenize();
 
-    expect(tokens[0].type).toBe(TokenType.NUMBER);
-    expect(tokens[0].value).toBe('42');
+    expect(tokens[0]?.type).toBe(TokenType.NUMBER);
+    expect(tokens[0]?.value).toBe('42');
 
-    expect(tokens[1].type).toBe(TokenType.NUMBER);
-    expect(tokens[1].value).toBe('3.14');
+    expect(tokens[1]?.type).toBe(TokenType.NUMBER);
+    expect(tokens[1]?.value).toBe('3.14');
   });
 
   it('should handle comments', () => {
@@ -49,10 +49,10 @@ describe('lexer', () => {
     const lexer = new Lexer(source);
     const tokens = lexer.tokenize();
 
-    expect(tokens[0].type).toBe(TokenType.COMMENT);
-    expect(tokens[0].value).toBe('// это комментарий');
+    expect(tokens[0]?.type).toBe(TokenType.COMMENT);
+    expect(tokens[0]?.value).toBe('// это комментарий');
 
-    expect(tokens[1].type).toBe(TokenType.QUEST);
+    expect(tokens[1]?.type).toBe(TokenType.QUEST);
   });
 
   it('should track line and column numbers', () => {
@@ -60,11 +60,11 @@ describe('lexer', () => {
     const lexer = new Lexer(source);
     const tokens = lexer.tokenize();
 
-    expect(tokens[0].line).toBe(1);
-    expect(tokens[0].column).toBe(1);
+    expect(tokens[0]?.line).toBe(1);
+    expect(tokens[0]?.column).toBe(1);
 
-    expect(tokens[1].line).toBe(2);
-    expect(tokens[1].column).toBe(1);
+    expect(tokens[1]?.line).toBe(2);
+    expect(tokens[1]?.column).toBe(1);
   });
 
   it('should handle all symbols', () => {
@@ -86,7 +86,7 @@ describe('lexer', () => {
     ];
 
     expectedTypes.forEach((expectedType, index) => {
-      expect(tokens[index].type).toBe(expectedType);
+      expect(tokens[index]?.type).toBe(expectedType);
     });
   });
 
diff --git a/src/__tests__/parser.test.ts b/src/__tests__/parser.test.ts
index 4c59781..59bd51d 100644
--- a/src/__tests__/parser.test.ts
+++ b/src/__tests__/parser.test.ts
@@ -59,10 +59,10 @@ describe('parser', () => {
 
     const nodes = ast.graph.nodes;
     expect(Object.keys(nodes)).toHaveLength(4);
-    expect(nodes.старт.nodeType).toBe('начальный');
-    expect(nodes.действие1.nodeType).toBe('действие');
-    expect(nodes.конец1.nodeType).toBe('концовка');
-    expect(nodes.конец2.nodeType).toBe('концовка');
+    expect(nodes.старт?.nodeType).toBe('начальный');
+    expect(nodes.действие1?.nodeType).toBe('действие');
+    expect(nodes.конец1?.nodeType).toBe('концовка');
+    expect(nodes.конец2?.nodeType).toBe('концовка');
   });
 
   it('should parse action node with options', () => {
diff --git a/src/ast.ts b/src/ast.ts
index 798d211..32b4ee3 100644
--- a/src/ast.ts
+++ b/src/ast.ts
@@ -6,7 +6,7 @@ export enum TokenType {
   IDENTIFIER = 'IDENTIFIER',
   STRING = 'STRING',
   NUMBER = 'NUMBER',
-  
+
   // Keywords
   QUEST = 'квест',
   GOAL = 'цель',
@@ -19,12 +19,12 @@ export enum TokenType {
   TRANSITIONS = 'переходы',
   OPTIONS = 'варианты',
   TITLE = 'название',
-  
+
   // Node types
   INITIAL = 'начальный',
   ACTION = 'действие',
   ENDING = 'концовка',
-  
+
   // Symbols
   SEMICOLON = ';',
   COLON = ':',
@@ -36,12 +36,12 @@ export enum TokenType {
   RIGHT_BRACKET = ']',
   LEFT_PAREN = '(',
   RIGHT_PAREN = ')',
-  
+
   // Special
   EOF = 'EOF',
   NEWLINE = 'NEWLINE',
   COMMENT = 'COMMENT',
-  WHITESPACE = 'WHITESPACE'
+  WHITESPACE = 'WHITESPACE',
 }
 
 /**
diff --git a/src/cli.ts b/src/cli.ts
index fe52791..e1e4296 100644
--- a/src/cli.ts
+++ b/src/cli.ts
@@ -1,9 +1,11 @@
 #!/usr/bin/env node
 
+import type { QuestInterpreter } from '.';
+import type { InitialNode, NodeDefinition } from './ast.js';
 import fs from 'node:fs';
+import process from 'node:process';
 import * as p from '@clack/prompts';
-import { QuestLang, type QuestInterpreter } from '.';
-import { type NodeDefinition, type InitialNode } from './ast';
+import { QuestLang } from '.';
 
 /**
  * Beautiful command-line interface for QuestLang using clack
@@ -14,9 +16,9 @@ class ClackCLI {
    */
   public async run(): Promise<void> {
     const args = process.argv.slice(2);
-    
+
     console.clear();
-    
+
     p.intro('🎮 QuestLang Interpreter');
 
     if (args.length === 0) {
@@ -25,32 +27,32 @@ class ClackCLI {
     }
 
     const command = args[0];
-    
+
     switch (command) {
       case 'play':
         if (args.length < 2) {
           p.outro('❌ Usage: questlang-clack play <file.ql>');
           process.exit(1);
         }
-        await this.playQuest(args[1]);
+        await this.playQuest(args[1]!);
         break;
-      
+
       case 'validate':
         if (args.length < 2) {
           p.outro('❌ Usage: questlang-clack validate <file.ql>');
           process.exit(1);
         }
-        await this.validateQuest(args[1]);
+        await this.validateQuest(args[1]!);
         break;
-      
+
       case 'analyze':
         if (args.length < 2) {
           p.outro('❌ Usage: questlang-clack analyze <file.ql>');
           process.exit(1);
         }
-        await this.analyzeQuest(args[1]);
+        await this.analyzeQuest(args[1]!);
         break;
-      
+
       default:
         p.outro(`❌ Unknown command: ${command}`);
         process.exit(1);
@@ -59,7 +61,7 @@ class ClackCLI {
 
   private async showInteractiveMenu(): Promise<void> {
     const questFiles = this.findQuestFiles();
-    
+
     if (questFiles.length === 0) {
       p.outro('❌ No .ql quest files found in current directory');
       process.exit(1);
@@ -107,25 +109,26 @@ class ClackCLI {
       return fs.readdirSync('.')
         .filter(file => file.endsWith('.ql'))
         .sort();
-    } catch {
+    }
+    catch {
       return [];
     }
   }
 
   private async playQuest(filename: string): Promise<void> {
     const spinner = p.spinner();
-    
+
     try {
       spinner.start('Loading quest...');
-      
+
       const source = this.readFile(filename);
       const interpreter = QuestLang.interpret(source);
-      
+
       // Validate first
       const validation = interpreter.validate();
       if (!validation.isValid) {
         spinner.stop('❌ Quest validation failed');
-        
+
         p.log.error('Validation errors:');
         validation.errors.forEach(error => p.log.error(`  • ${error}`));
         p.outro('Fix the errors and try again');
@@ -134,12 +137,12 @@ class ClackCLI {
 
       const questInfo = interpreter.getQuestInfo();
       spinner.stop('✅ Quest loaded successfully');
-      
+
       p.note(`📖 ${questInfo.goal}`, `🎮 ${questInfo.name}`);
 
       await this.gameLoop(interpreter);
-      
-    } catch (error) {
+    }
+    catch (error) {
       spinner.stop('❌ Error loading quest');
       p.log.error(error instanceof Error ? error.message : String(error));
       p.outro('Failed to start quest');
@@ -150,7 +153,7 @@ class ClackCLI {
   private async gameLoop(interpreter: QuestInterpreter): Promise<void> {
     while (!interpreter.getState().isComplete) {
       const currentNode = interpreter.getCurrentNode();
-      
+
       if (!currentNode) {
         p.log.error('Current node not found');
         break;
@@ -161,13 +164,13 @@ class ClackCLI {
 
       if (currentNode.nodeType === 'действие') {
         const choices = interpreter.getAvailableChoices();
-        
+
         const choice = await p.select({
           message: 'What do you want to do?',
           options: choices.map((choice, index) => ({
             value: index,
-            label: choice.text
-          }))
+            label: choice.text,
+          })),
         });
 
         if (p.isCancel(choice)) {
@@ -176,21 +179,28 @@ class ClackCLI {
         }
 
         const result = interpreter.executeChoice(choice as number);
-        
+
         if (!result.success) {
           p.log.error(`Error: ${result.error}`);
           break;
         }
-      } else if (currentNode.nodeType === 'начальный') {
+      }
+      else if (currentNode.nodeType === 'начальный') {
         // Auto-advance from initial nodes to first transition
         const initialNode = currentNode as InitialNode;
         if (initialNode.transitions && initialNode.transitions.length > 0) {
-          const result = interpreter.moveToNode(initialNode.transitions[0]);
+          const firstTransition = initialNode.transitions[0];
+          if (!firstTransition) {
+            p.log.error('First transition is undefined');
+            break;
+          }
+          const result = interpreter.moveToNode(firstTransition);
           if (!result.success) {
             p.log.error(`Error: ${result.error}`);
             break;
           }
-        } else {
+        }
+        else {
           p.log.error('Initial node has no transitions');
           break;
         }
@@ -203,9 +213,9 @@ class ClackCLI {
       const finalNode = interpreter.getCurrentNode();
       p.note(
         finalNode?.description || 'Quest completed',
-        `🏆 ${state.endingTitle}`
+        `🏆 ${state.endingTitle}`,
       );
-      
+
       const playAgain = await p.confirm({
         message: 'Would you like to play again?',
       });
@@ -213,7 +223,8 @@ class ClackCLI {
       if (!p.isCancel(playAgain) && playAgain) {
         interpreter.reset();
         await this.gameLoop(interpreter);
-      } else {
+      }
+      else {
         p.outro('Thanks for playing! 🎉');
       }
     }
@@ -221,26 +232,28 @@ class ClackCLI {
 
   private async validateQuest(filename: string): Promise<void> {
     const spinner = p.spinner();
-    
+
     try {
       spinner.start('Validating quest...');
-      
+
       const source = this.readFile(filename);
       const validation = QuestLang.validate(source);
-      
+
       if (validation.isValid) {
         spinner.stop('✅ Validation completed');
         p.log.success('Quest is valid!');
         p.outro('🎉 No issues found');
-      } else {
+      }
+      else {
         spinner.stop('❌ Validation failed');
-        
+
         p.log.error('Validation errors:');
         validation.errors.forEach(error => p.log.error(`  • ${error}`));
         p.outro('Fix the errors and try again');
         process.exit(1);
       }
-    } catch (error) {
+    }
+    catch (error) {
       spinner.stop('❌ Error during validation');
       p.log.error(error instanceof Error ? error.message : String(error));
       p.outro('Validation failed');
@@ -250,58 +263,59 @@ class ClackCLI {
 
   private async analyzeQuest(filename: string): Promise<void> {
     const spinner = p.spinner();
-    
+
     try {
       spinner.start('Analyzing quest...');
-      
+
       const source = this.readFile(filename);
       const interpreter = QuestLang.interpret(source);
       const questInfo = interpreter.getQuestInfo();
-      
+
       spinner.stop('✅ Analysis completed');
-      
+
       const nodes = Object.values(interpreter.getProgram().graph.nodes) as NodeDefinition[];
       const initialNodes = nodes.filter(n => n.nodeType === 'начальный');
       const actionNodes = nodes.filter(n => n.nodeType === 'действие');
       const endingNodes = nodes.filter(n => n.nodeType === 'концовка');
-      
+
       p.note(
-        `📊 Quest Analysis Results\n\n` +
-        `Total nodes: ${nodes.length}\n` +
-        `  • Initial nodes: ${initialNodes.length}\n` +
-        `  • Action nodes: ${actionNodes.length}\n` +
-        `  • Ending nodes: ${endingNodes.length}`,
-        `📖 ${questInfo.name}`
+        `📊 Quest Analysis Results\n\n`
+        + `Total nodes: ${nodes.length}\n`
+        + `  • Initial nodes: ${initialNodes.length}\n`
+        + `  • Action nodes: ${actionNodes.length}\n`
+        + `  • Ending nodes: ${endingNodes.length}`,
+        `📖 ${questInfo.name}`,
       );
-      
+
       // Analyze paths
       const paths = interpreter.getAllPaths();
-      
+
       if (paths.length > 0) {
         const avgPathLength = paths.reduce((sum, path) => sum + path.length, 0) / paths.length;
         const shortestPath = Math.min(...paths.map(path => path.length));
         const longestPath = Math.max(...paths.map(path => path.length));
-        
+
         p.log.info('📈 Path Analysis:');
         p.log.info(`  • Possible paths: ${paths.length}`);
         p.log.info(`  • Average path length: ${avgPathLength.toFixed(1)} steps`);
         p.log.info(`  • Shortest path: ${shortestPath} steps`);
         p.log.info(`  • Longest path: ${longestPath} steps`);
       }
-      
+
       // Validation
       const validation = interpreter.validate();
-      
+
       if (validation.isValid) {
         p.log.success('✅ Quest structure is valid');
         p.outro('🎉 Analysis completed successfully');
-      } else {
+      }
+      else {
         p.log.warn('⚠️  Quest has validation issues:');
         validation.errors.forEach(error => p.log.warn(`  • ${error}`));
         p.outro('Consider fixing these issues');
       }
-      
-    } catch (error) {
+    }
+    catch (error) {
       spinner.stop('❌ Error during analysis');
       p.log.error(error instanceof Error ? error.message : String(error));
       p.outro('Analysis failed');
@@ -313,14 +327,14 @@ class ClackCLI {
     if (!fs.existsSync(filename)) {
       throw new Error(`File not found: ${filename}`);
     }
-    
+
     return fs.readFileSync(filename, 'utf-8');
   }
 }
 
 const cli = new ClackCLI();
 
-cli.run().catch(error => {
+cli.run().catch((error) => {
   p.log.error(`Unexpected error: ${error}`);
   p.outro('❌ CLI crashed');
   process.exit(1);
diff --git a/src/index.ts b/src/index.ts
index 66f375e..b61f827 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,7 +1,7 @@
+import type { QuestProgram } from './ast';
+import { QuestInterpreter } from './interpreter';
 import { Lexer } from './lexer';
 import { Parser } from './parser';
-import { QuestInterpreter } from './interpreter';
-import type { QuestProgram } from './ast';
 
 /**
  * Main QuestLang processor
@@ -13,7 +13,7 @@ export class QuestLang {
   public static parse(source: string): QuestProgram {
     const lexer = new Lexer(source);
     const tokens = lexer.tokenize();
-    
+
     const parser = new Parser(tokens);
     return parser.parse();
   }
@@ -33,18 +33,17 @@ export class QuestLang {
     try {
       const interpreter = this.interpret(source);
       return interpreter.validate();
-    } catch (error) {
+    }
+    catch (error) {
       return {
         isValid: false,
-        errors: [error instanceof Error ? error.message : 'Unknown parsing error']
+        errors: [error instanceof Error ? error.message : 'Unknown parsing error'],
       };
     }
   }
 }
 
-// Re-export main classes
+export * from './ast';
+export { QuestInterpreter } from './interpreter';
 export { Lexer } from './lexer';
 export { Parser } from './parser';
-export { QuestInterpreter } from './interpreter';
-export * from './ast';
-export * from './types';
diff --git a/src/interpreter.ts b/src/interpreter.ts
index 93c80ee..23758de 100644
--- a/src/interpreter.ts
+++ b/src/interpreter.ts
@@ -1,11 +1,10 @@
 import type {
-  QuestProgram,
-  GraphNode,
-  NodeDefinition,
-  InitialNode,
   ActionNode,
   EndingNode,
-  OptionChoice
+  InitialNode,
+  NodeDefinition,
+  OptionChoice,
+  QuestProgram,
 } from './ast';
 
 /**
@@ -31,9 +30,9 @@ export interface ExecutionResult {
  * Visitor interface for quest nodes
  */
 export interface QuestVisitor {
-  visitInitialNode(node: InitialNode, state: QuestState): void;
-  visitActionNode(node: ActionNode, state: QuestState): void;
-  visitEndingNode(node: EndingNode, state: QuestState): void;
+  visitInitialNode: (node: InitialNode, state: QuestState) => void;
+  visitActionNode: (node: ActionNode, state: QuestState) => void;
+  visitEndingNode: (node: EndingNode, state: QuestState) => void;
 }
 
 /**
@@ -48,7 +47,7 @@ export class QuestInterpreter {
     this.currentState = {
       currentNode: program.graph.start,
       history: [],
-      isComplete: false
+      isComplete: false,
     };
   }
 
@@ -66,7 +65,7 @@ export class QuestInterpreter {
     return {
       name: this.program.name,
       goal: this.program.goal,
-      isComplete: this.currentState.isComplete
+      isComplete: this.currentState.isComplete,
     };
   }
 
@@ -101,12 +100,12 @@ export class QuestInterpreter {
    */
   public executeChoice(choiceIndex: number): ExecutionResult {
     const currentNode = this.getCurrentNode();
-    
+
     if (!currentNode) {
       return {
         success: false,
         newState: this.currentState,
-        error: `Current node '${this.currentState.currentNode}' not found`
+        error: `Current node '${this.currentState.currentNode}' not found`,
       };
     }
 
@@ -114,7 +113,7 @@ export class QuestInterpreter {
       return {
         success: false,
         newState: this.currentState,
-        error: `Cannot execute choice on node type '${currentNode.nodeType}'`
+        error: `Cannot execute choice on node type '${currentNode.nodeType}'`,
       };
     }
 
@@ -125,11 +124,18 @@ export class QuestInterpreter {
       return {
         success: false,
         newState: this.currentState,
-        error: `Invalid choice index: ${choiceIndex}. Available choices: 0-${choices.length - 1}`
+        error: `Invalid choice index: ${choiceIndex}. Available choices: 0-${choices.length - 1}`,
       };
     }
 
     const choice = choices[choiceIndex];
+    if (!choice) {
+      return {
+        success: false,
+        newState: this.currentState,
+        error: `Choice at index ${choiceIndex} is undefined`,
+      };
+    }
     return this.moveToNode(choice.target);
   }
 
@@ -138,12 +144,12 @@ export class QuestInterpreter {
    */
   public moveToNode(nodeId: string): ExecutionResult {
     const targetNode = this.program.graph.nodes[nodeId];
-    
+
     if (!targetNode) {
       return {
         success: false,
         newState: this.currentState,
-        error: `Target node '${nodeId}' not found`
+        error: `Target node '${nodeId}' not found`,
       };
     }
 
@@ -152,14 +158,14 @@ export class QuestInterpreter {
       currentNode: nodeId,
       history: [...this.currentState.history, this.currentState.currentNode],
       isComplete: targetNode.nodeType === 'концовка',
-      endingTitle: targetNode.nodeType === 'концовка' ? (targetNode as EndingNode).title : undefined
+      endingTitle: targetNode.nodeType === 'концовка' ? (targetNode as EndingNode).title : undefined,
     };
 
     this.currentState = newState;
 
     return {
       success: true,
-      newState: { ...newState }
+      newState: { ...newState },
     };
   }
 
@@ -170,7 +176,7 @@ export class QuestInterpreter {
     this.currentState = {
       currentNode: this.program.graph.start,
       history: [],
-      isComplete: false
+      isComplete: false,
     };
   }
 
@@ -180,15 +186,15 @@ export class QuestInterpreter {
   public getAllPaths(): string[][] {
     const paths: string[][] = [];
     const visited = new Set<string>();
-    
+
     this.findPaths(this.currentState.currentNode, [this.currentState.currentNode], paths, visited);
-    
+
     return paths;
   }
 
   private findPaths(nodeId: string, currentPath: string[], allPaths: string[][], visited: Set<string>): void {
     const node = this.program.graph.nodes[nodeId];
-    
+
     if (!node || visited.has(nodeId)) {
       return;
     }
@@ -205,7 +211,8 @@ export class QuestInterpreter {
       for (const option of actionNode.options) {
         this.findPaths(option.target, [...currentPath, option.target], allPaths, new Set(visited));
       }
-    } else if (node.nodeType === 'начальный') {
+    }
+    else if (node.nodeType === 'начальный') {
       const initialNode = node as InitialNode;
       for (const transition of initialNode.transitions) {
         this.findPaths(transition, [...currentPath, transition], allPaths, new Set(visited));
@@ -234,7 +241,8 @@ export class QuestInterpreter {
             errors.push(`Node '${nodeId}' references non-existent target '${option.target}'`);
           }
         }
-      } else if (node.nodeType === 'начальный') {
+      }
+      else if (node.nodeType === 'начальный') {
         const initialNode = node as InitialNode;
         for (const transition of initialNode.transitions) {
           if (!this.program.graph.nodes[transition]) {
@@ -247,7 +255,7 @@ export class QuestInterpreter {
     // Check for unreachable nodes
     const reachable = new Set<string>();
     this.findReachableNodes(this.program.graph.start, reachable);
-    
+
     for (const nodeId of nodeIds) {
       if (!reachable.has(nodeId)) {
         errors.push(`Node '${nodeId}' is unreachable`);
@@ -256,15 +264,17 @@ export class QuestInterpreter {
 
     return {
       isValid: errors.length === 0,
-      errors
+      errors,
     };
   }
 
   private findReachableNodes(nodeId: string, reachable: Set<string>): void {
-    if (reachable.has(nodeId)) return;
-    
+    if (reachable.has(nodeId))
+      return;
+
     const node = this.program.graph.nodes[nodeId];
-    if (!node) return;
+    if (!node)
+      return;
 
     reachable.add(nodeId);
 
@@ -273,7 +283,8 @@ export class QuestInterpreter {
       for (const option of actionNode.options) {
         this.findReachableNodes(option.target, reachable);
       }
-    } else if (node.nodeType === 'начальный') {
+    }
+    else if (node.nodeType === 'начальный') {
       const initialNode = node as InitialNode;
       for (const transition of initialNode.transitions) {
         this.findReachableNodes(transition, reachable);
diff --git a/src/lexer.ts b/src/lexer.ts
index 44c6950..1399cd6 100644
--- a/src/lexer.ts
+++ b/src/lexer.ts
@@ -1,5 +1,5 @@
+import type { Token } from './ast';
 import { TokenType } from './ast';
-import type { Token, Position } from './ast';
 
 /**
  * Lexical analyzer for QuestLang
@@ -26,7 +26,7 @@ export class Lexer {
     ['название', TokenType.TITLE],
     ['начальный', TokenType.INITIAL],
     ['действие', TokenType.ACTION],
-    ['концовка', TokenType.ENDING]
+    ['концовка', TokenType.ENDING],
   ]);
 
   constructor(source: string) {
@@ -100,7 +100,8 @@ export class Lexer {
       case '/':
         if (this.match('/')) {
           this.scanComment(start, startLine, startColumn);
-        } else {
+        }
+        else {
           throw new Error(`Unexpected character: ${c} at ${startLine}:${startColumn}`);
         }
         break;
@@ -110,9 +111,11 @@ export class Lexer {
       default:
         if (this.isDigit(c)) {
           this.scanNumber(start, startLine, startColumn);
-        } else if (this.isAlpha(c)) {
+        }
+        else if (this.isAlpha(c)) {
           this.scanIdentifier(start, startLine, startColumn);
-        } else {
+        }
+        else {
           throw new Error(`Unexpected character: ${c} at ${startLine}:${startColumn}`);
         }
         break;
@@ -182,7 +185,7 @@ export class Lexer {
       line: line || this.line,
       column: column || this.column,
       start: start || this.position,
-      end: this.position
+      end: this.position,
     });
   }
 
@@ -194,20 +197,24 @@ export class Lexer {
   }
 
   private match(expected: string): boolean {
-    if (this.isAtEnd()) return false;
-    if (this.source.charAt(this.position) !== expected) return false;
+    if (this.isAtEnd())
+      return false;
+    if (this.source.charAt(this.position) !== expected)
+      return false;
     this.position++;
     this.column++;
     return true;
   }
 
   private peek(): string {
-    if (this.isAtEnd()) return '\0';
+    if (this.isAtEnd())
+      return '\0';
     return this.source.charAt(this.position);
   }
 
   private peekNext(): string {
-    if (this.position + 1 >= this.source.length) return '\0';
+    if (this.position + 1 >= this.source.length)
+      return '\0';
     return this.source.charAt(this.position + 1);
   }
 
@@ -220,12 +227,12 @@ export class Lexer {
   }
 
   private isAlpha(c: string): boolean {
-    return (c >= 'a' && c <= 'z') ||
-           (c >= 'A' && c <= 'Z') ||
-           (c >= 'а' && c <= 'я') ||
-           (c >= 'А' && c <= 'Я') ||
-           c === 'ё' || c === 'Ё' ||
-           c === '_';
+    return (c >= 'a' && c <= 'z')
+      || (c >= 'A' && c <= 'Z')
+      || (c >= 'а' && c <= 'я')
+      || (c >= 'А' && c <= 'Я')
+      || c === 'ё' || c === 'Ё'
+      || c === '_';
   }
 
   private isAlphaNumeric(c: string): boolean {
diff --git a/src/parser.ts b/src/parser.ts
index 0d7bf4f..45fde7e 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -1,17 +1,5 @@
+import type { ActionNode, EndingNode, GraphNode, InitialNode, NodeDefinition, OptionChoice, QuestProgram, Token } from './ast';
 import { TokenType } from './ast';
-import type { Token } from './ast';
-import type {
-  ASTNode,
-  QuestProgram,
-  GraphNode,
-  NodeDefinition,
-  InitialNode,
-  ActionNode,
-  EndingNode,
-  OptionChoice,
-  StringLiteral,
-  Identifier
-} from './ast';
 
 /**
  * Parser for QuestLang
@@ -22,9 +10,9 @@ export class Parser {
 
   constructor(tokens: Token[]) {
     // Filter out comments and whitespace
-    this.tokens = tokens.filter(token => 
-      token.type !== TokenType.COMMENT && 
-      token.type !== TokenType.WHITESPACE
+    this.tokens = tokens.filter(token =>
+      token.type !== TokenType.COMMENT
+      && token.type !== TokenType.WHITESPACE,
     );
   }
 
@@ -36,15 +24,15 @@ export class Parser {
   }
 
   private parseQuest(): QuestProgram {
-    const questToken = this.consume(TokenType.QUEST, "Expected 'квест'");
-    const name = this.consume(TokenType.IDENTIFIER, "Expected quest name").value;
-    this.consume(TokenType.SEMICOLON, "Expected ';' after quest name");
+    const questToken = this.consume(TokenType.QUEST, 'Expected \'квест\'');
+    const name = this.consume(TokenType.IDENTIFIER, 'Expected quest name').value;
+    this.consume(TokenType.SEMICOLON, 'Expected \';\' after quest name');
 
     const goal = this.parseGoal();
     const graph = this.parseGraph();
 
-    this.consume(TokenType.END, "Expected 'конец'");
-    this.consume(TokenType.SEMICOLON, "Expected ';' after 'конец'");
+    this.consume(TokenType.END, 'Expected \'конец\'');
+    this.consume(TokenType.SEMICOLON, 'Expected \';\' after \'конец\'');
 
     return {
       type: 'QuestProgram',
@@ -52,20 +40,20 @@ export class Parser {
       goal,
       graph,
       line: questToken.line,
-      column: questToken.column
+      column: questToken.column,
     };
   }
 
   private parseGoal(): string {
-    this.consume(TokenType.GOAL, "Expected 'цель'");
-    const goalValue = this.consume(TokenType.STRING, "Expected goal description").value;
-    this.consume(TokenType.SEMICOLON, "Expected ';' after goal");
+    this.consume(TokenType.GOAL, 'Expected \'цель\'');
+    const goalValue = this.consume(TokenType.STRING, 'Expected goal description').value;
+    this.consume(TokenType.SEMICOLON, 'Expected \';\' after goal');
     return goalValue;
   }
 
   private parseGraph(): GraphNode {
-    const graphToken = this.consume(TokenType.GRAPH, "Expected 'граф'");
-    this.consume(TokenType.LEFT_BRACE, "Expected '{' after 'граф'");
+    const graphToken = this.consume(TokenType.GRAPH, 'Expected \'граф\'');
+    this.consume(TokenType.LEFT_BRACE, 'Expected \'{\' after \'граф\'');
 
     const nodes: Record<string, NodeDefinition> = {};
     let start = '';
@@ -73,41 +61,43 @@ export class Parser {
     while (!this.check(TokenType.RIGHT_BRACE) && !this.isAtEnd()) {
       if (this.match(TokenType.NODES)) {
         this.parseNodes(nodes);
-      } else if (this.match(TokenType.START)) {
-        this.consume(TokenType.COLON, "Expected ':' after 'начало'");
-        start = this.consume(TokenType.IDENTIFIER, "Expected start node identifier").value;
-        this.consume(TokenType.SEMICOLON, "Expected ';' after start node");
-      } else {
+      }
+      else if (this.match(TokenType.START)) {
+        this.consume(TokenType.COLON, 'Expected \':\' after \'начало\'');
+        start = this.consume(TokenType.IDENTIFIER, 'Expected start node identifier').value;
+        this.consume(TokenType.SEMICOLON, 'Expected \';\' after start node');
+      }
+      else {
         throw new Error(`Unexpected token in graph: ${this.peek().type} at ${this.peek().line}:${this.peek().column}`);
       }
     }
 
-    this.consume(TokenType.RIGHT_BRACE, "Expected '}' after graph body");
+    this.consume(TokenType.RIGHT_BRACE, 'Expected \'}\' after graph body');
 
     return {
       type: 'Graph',
       nodes,
       start,
       line: graphToken.line,
-      column: graphToken.column
+      column: graphToken.column,
     };
   }
 
   private parseNodes(nodes: Record<string, NodeDefinition>): void {
-    this.consume(TokenType.LEFT_BRACE, "Expected '{' after 'узлы'");
+    this.consume(TokenType.LEFT_BRACE, 'Expected \'{\' after \'узлы\'');
 
     while (!this.check(TokenType.RIGHT_BRACE) && !this.isAtEnd()) {
-      const nodeId = this.consume(TokenType.IDENTIFIER, "Expected node identifier").value;
-      this.consume(TokenType.COLON, "Expected ':' after node identifier");
-      this.consume(TokenType.LEFT_BRACE, "Expected '{' after node identifier");
+      const nodeId = this.consume(TokenType.IDENTIFIER, 'Expected node identifier').value;
+      this.consume(TokenType.COLON, 'Expected \':\' after node identifier');
+      this.consume(TokenType.LEFT_BRACE, 'Expected \'{\' after node identifier');
 
       const node = this.parseNodeDefinition(nodeId);
       nodes[nodeId] = node;
 
-      this.consume(TokenType.RIGHT_BRACE, "Expected '}' after node definition");
+      this.consume(TokenType.RIGHT_BRACE, 'Expected \'}\' after node definition');
     }
 
-    this.consume(TokenType.RIGHT_BRACE, "Expected '}' after nodes");
+    this.consume(TokenType.RIGHT_BRACE, 'Expected \'}\' after nodes');
   }
 
   private parseNodeDefinition(id: string): NodeDefinition {
@@ -120,33 +110,41 @@ export class Parser {
 
     while (!this.check(TokenType.RIGHT_BRACE) && !this.isAtEnd()) {
       if (this.match(TokenType.TYPE)) {
-        this.consume(TokenType.COLON, "Expected ':' after 'тип'");
+        this.consume(TokenType.COLON, 'Expected \':\' after \'тип\'');
         const typeToken = this.advance();
         if (typeToken.type === TokenType.INITIAL) {
           nodeType = 'начальный';
-        } else if (typeToken.type === TokenType.ACTION) {
+        }
+        else if (typeToken.type === TokenType.ACTION) {
           nodeType = 'действие';
-        } else if (typeToken.type === TokenType.ENDING) {
+        }
+        else if (typeToken.type === TokenType.ENDING) {
           nodeType = 'концовка';
-        } else {
+        }
+        else {
           throw new Error(`Invalid node type: ${typeToken.value} at ${typeToken.line}:${typeToken.column}`);
         }
-        this.consume(TokenType.SEMICOLON, "Expected ';' after node type");
-      } else if (this.match(TokenType.DESCRIPTION)) {
-        this.consume(TokenType.COLON, "Expected ':' after 'описание'");
-        description = this.consume(TokenType.STRING, "Expected description string").value;
-        this.consume(TokenType.SEMICOLON, "Expected ';' after description");
-      } else if (this.match(TokenType.TRANSITIONS)) {
-        this.consume(TokenType.COLON, "Expected ':' after 'переходы'");
+        this.consume(TokenType.SEMICOLON, 'Expected \';\' after node type');
+      }
+      else if (this.match(TokenType.DESCRIPTION)) {
+        this.consume(TokenType.COLON, 'Expected \':\' after \'описание\'');
+        description = this.consume(TokenType.STRING, 'Expected description string').value;
+        this.consume(TokenType.SEMICOLON, 'Expected \';\' after description');
+      }
+      else if (this.match(TokenType.TRANSITIONS)) {
+        this.consume(TokenType.COLON, 'Expected \':\' after \'переходы\'');
         this.parseTransitions(transitions);
-      } else if (this.match(TokenType.OPTIONS)) {
-        this.consume(TokenType.COLON, "Expected ':' after 'варианты'");
+      }
+      else if (this.match(TokenType.OPTIONS)) {
+        this.consume(TokenType.COLON, 'Expected \':\' after \'варианты\'');
         this.parseOptions(options);
-      } else if (this.match(TokenType.TITLE)) {
-        this.consume(TokenType.COLON, "Expected ':' after 'название'");
-        title = this.consume(TokenType.STRING, "Expected title string").value;
-        this.consume(TokenType.SEMICOLON, "Expected ';' after title");
-      } else {
+      }
+      else if (this.match(TokenType.TITLE)) {
+        this.consume(TokenType.COLON, 'Expected \':\' after \'название\'');
+        title = this.consume(TokenType.STRING, 'Expected title string').value;
+        this.consume(TokenType.SEMICOLON, 'Expected \';\' after title');
+      }
+      else {
         throw new Error(`Unexpected token in node definition: ${this.peek().type} at ${this.peek().line}:${this.peek().column}`);
       }
     }
@@ -157,7 +155,7 @@ export class Parser {
       nodeType,
       description,
       line: startToken.line,
-      column: startToken.column
+      column: startToken.column,
     };
 
     switch (nodeType) {
@@ -165,61 +163,61 @@ export class Parser {
         return {
           ...baseNode,
           type: 'InitialNode',
-          transitions
+          transitions,
         } as InitialNode;
       case 'действие':
         return {
           ...baseNode,
           type: 'ActionNode',
-          options
+          options,
         } as ActionNode;
       case 'концовка':
         return {
           ...baseNode,
           type: 'EndingNode',
-          title
+          title,
         } as EndingNode;
     }
   }
 
   private parseTransitions(transitions: string[]): void {
-    this.consume(TokenType.LEFT_BRACKET, "Expected '[' for transitions");
-    
+    this.consume(TokenType.LEFT_BRACKET, 'Expected \'[\' for transitions');
+
     if (!this.check(TokenType.RIGHT_BRACKET)) {
       do {
-        const transition = this.consume(TokenType.IDENTIFIER, "Expected transition identifier").value;
+        const transition = this.consume(TokenType.IDENTIFIER, 'Expected transition identifier').value;
         transitions.push(transition);
       } while (this.match(TokenType.COMMA));
     }
 
-    this.consume(TokenType.RIGHT_BRACKET, "Expected ']' after transitions");
-    this.consume(TokenType.SEMICOLON, "Expected ';' after transitions");
+    this.consume(TokenType.RIGHT_BRACKET, 'Expected \']\' after transitions');
+    this.consume(TokenType.SEMICOLON, 'Expected \';\' after transitions');
   }
 
   private parseOptions(options: OptionChoice[]): void {
-    this.consume(TokenType.LEFT_BRACKET, "Expected '[' for options");
-    
+    this.consume(TokenType.LEFT_BRACKET, 'Expected \'[\' for options');
+
     if (!this.check(TokenType.RIGHT_BRACKET)) {
       do {
         const optionToken = this.peek();
-        this.consume(TokenType.LEFT_PAREN, "Expected '(' for option");
-        const text = this.consume(TokenType.STRING, "Expected option text").value;
-        this.consume(TokenType.COMMA, "Expected ',' in option");
-        const target = this.consume(TokenType.IDENTIFIER, "Expected target identifier").value;
-        this.consume(TokenType.RIGHT_PAREN, "Expected ')' after option");
+        this.consume(TokenType.LEFT_PAREN, 'Expected \'(\' for option');
+        const text = this.consume(TokenType.STRING, 'Expected option text').value;
+        this.consume(TokenType.COMMA, 'Expected \',\' in option');
+        const target = this.consume(TokenType.IDENTIFIER, 'Expected target identifier').value;
+        this.consume(TokenType.RIGHT_PAREN, 'Expected \')\' after option');
 
         options.push({
           type: 'OptionChoice',
           text,
           target,
           line: optionToken.line,
-          column: optionToken.column
+          column: optionToken.column,
         });
       } while (this.match(TokenType.COMMA));
     }
 
-    this.consume(TokenType.RIGHT_BRACKET, "Expected ']' after options");
-    this.consume(TokenType.SEMICOLON, "Expected ';' after options");
+    this.consume(TokenType.RIGHT_BRACKET, 'Expected \']\' after options');
+    this.consume(TokenType.SEMICOLON, 'Expected \';\' after options');
   }
 
   private match(...types: TokenType[]): boolean {
@@ -233,12 +231,14 @@ export class Parser {
   }
 
   private check(type: TokenType): boolean {
-    if (this.isAtEnd()) return false;
+    if (this.isAtEnd())
+      return false;
     return this.peek().type === type;
   }
 
   private advance(): Token {
-    if (!this.isAtEnd()) this.current++;
+    if (!this.isAtEnd())
+      this.current++;
     return this.previous();
   }
 
@@ -247,16 +247,17 @@ export class Parser {
   }
 
   private peek(): Token {
-    return this.tokens[this.current];
+    return this.tokens[this.current] || { type: TokenType.EOF, value: '', line: 0, column: 0, start: 0, end: 0 };
   }
 
   private previous(): Token {
-    return this.tokens[this.current - 1];
+    return this.tokens[this.current - 1] || { type: TokenType.EOF, value: '', line: 0, column: 0, start: 0, end: 0 };
   }
 
   private consume(type: TokenType, message: string): Token {
-    if (this.check(type)) return this.advance();
-    
+    if (this.check(type))
+      return this.advance();
+
     const current = this.peek();
     throw new Error(`${message}. Got ${current.type} at ${current.line}:${current.column}`);
   }
diff --git a/tsdown.config.ts b/tsdown.config.ts
index 15f5de8..8b5271c 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -8,5 +8,6 @@ export default defineConfig([
   {
     entry: 'src/cli.ts',
     noExternal: ['@clack/prompts'],
+    minify: true,
   },
-]);
\ No newline at end of file
+]);