A six-sentence / Once upon a time

This week in writing we wrote a six-sentence story about creating a character and adding detail. Our focus was on creating sentences. We learnt that the four criteria of a sentence are...
1. Our sentence must have one idea.
2. Our sentence must make sense.
3. Our sentence starts with a capital letter and ends with a full stop.
4. Our sentence leaves one space between each word.
I found how to plan is the hardest and I found how to write the sentences is the easiest.