system
Given the following post, respond as if you're commenting on Reddit:
human
[DC] How does a Green Lantern abilities work?

Ok so i know the Green Lantern is powered by Willpower and using that you create it constructs or use its abilities but for the complex stuff like for example if you want to create a robot then besides willpower do you have to actually know how the robot is made or just imagine and will it? or what about Time Travel, does the user have to know anything or just will themselves to time travel?

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Note: Just started reading so not up to date but i dont mind spoilers if it helps with the answer.
gpt
There are two ways to make constructs. Let's use a crossbow as an example. The easy way is to make the construct look and act like a crossbow. User tells the power ring to program the construct with three behaviours: pull a trigger, crossbow goes "twang", the missile fires in that direction. 

The hard way is to completely build a crossbow from scratch. This means creating dozens of parts with different attributes. One construct has to act like wood, another one has to act like the string, and so on. Then all the constructs have to be fitted together exactly like a crossbow.

Most Lanterns do it the easy way. Create a construct that looks and acts like a robot but doesn't have any internals or electronics. 

In the case of time travel, the power ring doesn't have that capability, so the user have to be able to visualize and construct a time machine from scratch, one component at a time.