# Space Exploration 4

**Title:** Исследуй Планету
**Subtitle:** Собери ресурсы, решая примеры!
**Footer bubble:** Итого собрано ресурсов:

## Layout

- 2 columns, 20 problems per page
- Icons: pack1 (pages 1–6), pack2 (pages 7–9)

## Problem Pattern

A ± B, where:
- B is from 1 to 10
- Result is from 1 to 29
- Each problem crosses a 10-boundary: either 10 or 20 (strictly, not just touching)

Types:
- Add crossing 10: A ∈ [1,9], B such that A+B ∈ [11,29]
- Add crossing 20: A ∈ [11,19], B such that A+B ∈ [21,29]
- Sub crossing 10: A ∈ [11,19], B such that A−B ∈ [1,9]
- Sub crossing 20: A ∈ [21,29], B such that A−B ∈ [11,19]

All 4 types are mixed randomly on every page.

## Pages

### Page 1 (pack1)
- **Hero:** spaceship1.jpeg, direction: row-reverse

### Page 2 (pack1)
- **Hero:** spaceship2.jpeg, direction: row

### Page 3 (pack1)
- **Hero:** spaceship3.png, direction: row-reverse

### Page 4 (pack1)
- **Hero:** spaceship4.jpeg, direction: row

### Page 5 (pack1)
- **Hero:** spaceship5.jpeg, direction: row-reverse

### Page 6 (pack1)
- **Hero:** spaceship6.jpeg, direction: row

### Page 7 (pack2)
- **Hero:** spaceship7.jpeg, direction: row-reverse

### Page 8 (pack2)
- **Hero:** spaceship8.jpeg, direction: row

### Page 9 (pack2)
- **Hero:** spaceship9.jpeg, direction: row-reverse