diff --git a/src/ast-builder.js b/src/ast-builder.js
new file mode 100644
index 0000000..65f2b32
--- /dev/null
+++ b/src/ast-builder.js
@@ -0,0 +1,126 @@
+import { parser } from './parser.js';
+
+const BaseHiVisitor = parser.getBaseCstVisitorConstructor();
+
+class AstBuilder extends BaseHiVisitor {
+    constructor() {
+        super();
+        this.validateVisitor();
+    }
+    
+    program(ctx) {
+        return { type: 'Program', body: this.visit(ctx.statements) };
+    }
+    
+    statements(ctx) {
+        return ctx.statement?.map(stmt => this.visit(stmt)) || [];
+    }
+
+    statement(ctx) {
+        if (ctx.declaration) return this.visit(ctx.declaration);
+        if (ctx.assignment) return this.visit(ctx.assignment);
+        if (ctx.expressionStatement) return this.visit(ctx.expressionStatement);
+    }
+    
+    expressionStatement(ctx) {
+        return { type: 'ExpressionStatement', expression: this.visit(ctx.expression) };
+    }
+
+    declaration(ctx) {
+        return {
+            type: 'VariableDeclaration',
+            identifier: ctx.Identifier[0].image,
+            value: this.visit(ctx.expression),
+        };
+    }
+
+    assignment(ctx) {
+        return {
+            type: 'Assignment',
+            identifier: ctx.Identifier[0].image,
+            value: this.visit(ctx.expression),
+        };
+    }
+    
+    expression(ctx) {
+        return this.visit(ctx.additiveExpression);
+    }
+
+    additiveExpression(ctx) {
+        let left = this.visit(ctx.left);
+        if (ctx.right) {
+            ctx.right.forEach((rhs) => {
+                left = {
+                    type: 'BinaryExpression',
+                    operator: '+',
+                    left: left,
+                    right: this.visit(rhs),
+                };
+            });
+        }
+        return left;
+    }
+
+    callExpression(ctx) {
+        let callee = this.visit(ctx.memberExpression);
+        if (ctx.LParen) {
+            return {
+                type: 'CallExpression',
+                callee: callee,
+                arguments: ctx.argumentList ? this.visit(ctx.argumentList) : [],
+            };
+        }
+        return callee;
+    }
+    
+    argumentList(ctx) {
+        return ctx.expression.map(expr => this.visit(expr));
+    }
+    
+    memberExpression(ctx) {
+        let obj = this.visit(ctx.primary);
+        if (ctx.Identifier) {
+            ctx.Identifier.forEach(propIdent => {
+                obj = {
+                    type: 'MemberExpression',
+                    object: obj,
+                    property: { type: 'Identifier', name: propIdent.image },
+                };
+            });
+        }
+        return obj;
+    }
+
+    primary(ctx) {
+        if (ctx.literal) return this.visit(ctx.literal);
+        if (ctx.Identifier) return { type: 'Identifier', name: ctx.Identifier[0].image };
+        if (ctx.block) return this.visit(ctx.block);
+        if (ctx.expression) return this.visit(ctx.expression);
+    }
+    
+    literal(ctx) {
+        if (ctx.Number) return { type: 'NumericLiteral', value: Number(ctx.Number[0].image) };
+        if (ctx.String) return { type: 'StringLiteral', value: ctx.String[0].image };
+    }
+
+    block(ctx) {
+        return {
+            type: 'Block',
+            properties: ctx.keyValuePairs ? this.visit(ctx.keyValuePairs) : []
+        };
+    }
+    
+    keyValuePairs(ctx) {
+        return ctx.keyValuePair.map(kv => this.visit(kv));
+    }
+    
+    keyValuePair(ctx) {
+        return {
+            type: 'Property',
+            key: ctx.Identifier[0].image,
+            value: this.visit(ctx.expression)
+        };
+    }
+}
+
+export const astBuilder = new AstBuilder();