Subject + predicate as topic and prepositional phrases I found this sentence while doing some listening practice:
长时间看电脑，对眼睛不好。
At first, I didn't understand why 长时间, expressing duration, is at the beginning of the sentence acting as topic 长时间看电脑, since I learned that these are usually placed at the end of the sentence or between the verb and the object (depending on whether the verb is transitive or not). I tried asking online and it turns out that when a sentence acts as a topic of a sentence, the word order can be quite different. I got other example sentences:
在罗马待的一个星期给我留下了很深的印象。
三年的汉语学习使我能和中国人流利地交流。
Is this a matter of pure habit or are there some strict rules governing word order in sentences that act as a topic?
Your subject of the sentence could be anything, as long as you make it clear to the listeners what it is.
After breaking down these sentences, you could see that Mandarin and English just have the order of their SUBJECT and subject description reversed.
Mandarin Structure
(Short description to describe the subject/event) + (SUBJECT/EVENT) + (Outcome of the event)
English Structure
(SUBJECT/EVENT) + (Short description to describe the subject/event) + (Outcome of the event)

长时间 + 看电脑 + 对眼睛不好。 Looking at a computer + for a long time + is bad for the eyes.
在罗马待的 + 一个星期 + 给我留下了很深的印象。 The week + stayed in Rome + gave me
deep impression.
三年的 + 汉语学习 + 使我能和中国人流利地交流。 Learning Mandarin + for three
years + made me able to communicate with Chinese fluently.

In general, as long as you don't make the first part too long -&gt; (Short description to describe the subject/event), then people will be able to understand the (SUBJECT/EVENT) you're trying to tell..but even the example below would work:

三年內每天一百下伏地挺身,一百下仰臥起坐,一百下深蹲,十公里跑步的 + 這種健身方式 + 讓他最後變成了禿頭。
The workout routine of 100 push-ups, 100 sit-ups, 100 squats, and 10km running for
three years eventually made him bald.

Just create more sentences of your own to practice, then you'll get the idea.