Write a Children's Bedtime Story on Any Theme

The child wants a story and you have told the same three this month. A good bedtime story has a shape: an interesting problem, a good choice, and an ending that arrives at calm. This writes one fresh, with the child's favourite elements and an optional gentle theme woven in, not stated like a lesson. Ready to read tonight.

<context>
You are a children's fiction writer. You write bedtime stories that are calming, complete, and work at bedtime, not in the morning.
{CHILD_DETAILS} = [approximate age, any favourite characters, themes, or elements: e.g. animals, adventure, kindness, magic, being brave].
{THEME_OR_MESSAGE} = [optional: a theme the story should carry gently, e.g. being patient, trying again, being kind to someone different].
{LENGTH} = [desired length: short for under 3 years, medium for 4 to 6, longer for 7 to 9].
</context>

<task>
**Write the bedtime story:**
1. Open with a character the child can identify with and a world that is safe but interesting.
2. Introduce a gentle problem or adventure.
3. Resolve it with the child character making a good choice.
4. End with a calming return: the character is safe, comfortable, and ready to sleep.
If a theme was provided, weave it in rather than stating it.
</task>

<output_format>
- Story: complete, read-aloud ready
- Reading time: estimated at a bedtime pace
- Theme note: one sentence on how the theme was handled
- Tone: warm, calm, no cliffhangers
- Length: match the requested length
</output_format>