## ADDED Requirements

### Requirement: Study only from local courses
The iPad app SHALL open study sessions only from locally downloaded courses (or their recent/session records). The app MUST NOT provide a path to compose a new lesson by picking arbitrary library files on device.

#### Scenario: No freeform composition
- **WHEN** the user is on child learning surfaces
- **THEN** there is no Explorer multi-select or album-draft flow to create a new study mode from raw files

### Requirement: Supported study modes
Study playback SHALL support at least `single_video`, `single_audio`, `single_pdf`, `video_pdf`, and `pdf_audio` for resources contained in a local course pack.

#### Scenario: Video plus PDF item
- **WHEN** the user starts a combo item with mode `video_pdf` and both files exist locally
- **THEN** Study shows a split layout bound to those pack media files

### Requirement: Orientation-driven split layout
For split modes (`video_pdf`, `pdf_audio`), the app SHALL choose layout from the study stage size: when width is greater than or equal to height, panes SHALL be side by side; otherwise panes SHALL be stacked. The app MUST NOT require the user to manually pick “左右分屏 / 上下分屏”. Split ratio SHALL be adjusted by dragging the stage divider, not by a separate slider control.

#### Scenario: Landscape uses side-by-side
- **WHEN** the study stage is wider than tall in a split mode
- **THEN** primary and secondary panes are arranged horizontally

#### Scenario: Portrait uses stacked
- **WHEN** the study stage is taller than wide in a split mode
- **THEN** primary and secondary panes are arranged vertically

#### Scenario: Divider drag changes ratio
- **WHEN** the user drags the stage divider
- **THEN** the relative pane sizes update according to the drag

### Requirement: Study chrome icons
Study SHALL provide a leading back control that is icon-only (no back title text) and trailing icon actions for PDF previous page, PDF next page (when a PDF pane exists), and collapse/expand of the secondary stage (when in a split mode). The study chrome MUST NOT show a mode label strip such as `video + pdf` and MUST NOT require a dedicated “保存进度” button.

#### Scenario: Icon toolbar
- **WHEN** the user is in Study for a `video_pdf` item
- **THEN** trailing icons include previous page, next page, and secondary-stage collapse/expand

### Requirement: Multi-item course entry
When a local course contains more than one study item, the app SHALL let the user choose an item before or within study entry. When a course contains exactly one item, tapping the course MAY open that item directly.

#### Scenario: Single-item direct open
- **WHEN** the user taps a downloaded course that has exactly one item
- **THEN** Study opens that item without requiring an extra composition step

#### Scenario: Multi-item picker
- **WHEN** the user taps a downloaded course that has multiple items
- **THEN** the app presents an item list and opens Study for the chosen item

### Requirement: Automatic local progress persistence
The app SHALL persist study progress (including media time, PDF page, split ratio, and orientation as applicable) locally on the iPad. Persistence SHALL run on user interaction with the study surface, on a timer of at most sixty seconds while Study is active, and when leaving Study or backgrounding the app. Progress MUST NOT be required to sync to the PC for MVP.

#### Scenario: Resume after relaunch
- **WHEN** the user studies an item, leaves the app, and later reopens the same recent entry
- **THEN** saved progress fields are available and applied in Study

#### Scenario: Periodic save
- **WHEN** Study remains active for sixty seconds
- **THEN** current media time and PDF page (as applicable) are persisted without a manual save action

### Requirement: No parent library management in study path
Study and home learning paths MUST NOT expose folder create/rename/move/delete of a general media library as part of the child learning flow.

#### Scenario: No explorer chrome in study
- **WHEN** the user enters Study from the home deck or recent row
- **THEN** the UI is a learning stage (playback/PDF) without library management chrome