---
generated_by: gdlink-build
generated_at: 2026-06-23T12:34:28Z
do_not_edit: true
title: Expression
brick_type: gate
tier: Basic
generated: true
---
# Expression
**Category:** Gate
**Tier:** Basic
## Purpose
Evaluates custom boolean expressions with complex logic, allowing arbitrary combinations beyond simple AND/OR/XOR gates.
## Visual Reference
```{raw} html
```
## When To Use
- Complex AI decisions with many conditions
- Multi-step puzzles (if A and B, or if C but not D)
- Advanced state machines
- Formula-based logic
- Replacing chains of controllers with single expression
## Runtime Behavior
**Triggers**: When the boolean expression evaluates to TRUE
```{raw} html
```
## Properties
| Property | Type | Default | Notes |
|---|---|---|---|
| Expression | string | True | Boolean expression (e.g., 'True', 'False', or GDScript expression) |
## Example Use Cases
**Complex Door Unlock**:
```
Expression: (key_red AND key_blue) OR (lever1 AND lever2 AND lever3)
// Door opens if have both keys OR all 3 levers pulled
```
**AI Attack Decision**:
```
Expression: can_see_player AND (health > 50 OR has_backup) AND NOT retreating
// Attack if see player AND (healthy OR has backup) AND not retreating
```
**Puzzle Solution**:
```
Expression: (switch1 XOR switch2) AND switch3 AND NOT switch4
// Puzzle solved if switches in specific pattern
```
