# Countdown

> Build a countdown timer that tests your React fundamentals by handling state, side effects, and precise time-based updates under real-world conditions.

- Difficulty: beginner
- Tags: useState, useEffect
- Estimated time: 30 minutes
- Tests: 6
- Requires subscription: no

## Overview

Build a countdown timer that tests your React fundamentals by handling state, side effects, and precise time-based updates under real-world conditions.


## Requirements

- Render the `Countdown` component inside `App`.
- The countdown must start from `INIT_COUNT` (in seconds) when the app loads.
- The remaining time must update every second and be displayed in `mm:ss` format.
- Clicking the **Pause / Play** button must pause and resume the countdown without resetting it.
- When the countdown reaches `0`, it must stop completely and never go into negative values.
- When the countdown finishes, the title must change from **"Countdown"** to **"Finished"**.


## Notes

- Think about which props the `<Countdown />` component should receive to allow pausing, reacting when it finishes, and starting from a specific value.
- Some tests may pass initially due to the initial render state.
- You may use the `timeToString` function located in `utils.ts` to format the remaining time.
- Be careful not to create unnecessary intervals.
- Remember to clean up side effects when the component updates or unmounts.


## Tests

01. renders the countdown componente
02. display the initial count
03. display the correct time after 1 second
04. pauses the countdown when the pause button is clicked
05. changes the title to 'Finished' when the countdown reaches 0
06. stops at 0 and does not go into negative values