# Spec Delta

## Purpose

Defines how the arena default size is derived from the output and how resizing affects the grid.

## ADDED Requirements

### Requirement: Default arena is about 80% of output
The system SHALL compute the default logical window size as 80% of the output mode dimensions divided by the active scale.

#### Scenario: Output available
- **WHEN** output mode and scale are known at startup
- **THEN** the default logical window size is approximately 80% of the output

### Requirement: Fallback when output unknown
The system SHALL use a fallback default size when output info is unavailable.

#### Scenario: No output info
- **WHEN** output mode is not reported
- **THEN** a fallback logical size is used

### Requirement: Cell size remains 8 logical pixels
The system SHALL keep an 8 logical pixel cell size.

#### Scenario: Grid dimensions
- **WHEN** the logical window size is known
- **THEN** grid columns and rows are logical size divided by 8

### Requirement: Resizable window
The system SHALL allow the window to be resized by the user.

#### Scenario: Resize
- **WHEN** the user resizes the window
- **THEN** the grid dimensions update accordingly

### Requirement: Grid preserved on resize
The system SHALL preserve overlapping cells when the grid dimensions change.

#### Scenario: Enlarge
- **WHEN** the window grows
- **THEN** existing cells within the old bounds remain