A lot of this has been explained in narration at various points in time, but I realize not everyone reads everything, and quite a bit of it was a long time ago.  So this post is going to hopefully provide a definitive central resource for the topic.

What is a 'mindfeeling'?
Mindfeeling is Luka's primary riftpower.  It is essentially a psychic awareness of who is around her at any given moment. 

How does it work?
Luka is always intuitively aware of all thinking beings around her in a radius of around 20 feet.  She feels this in her head like mental pressures and currents.  However, if she concentrates, she can both extend this range and mentally visualize the mindfeelings she feels similar to a HUD (like in video games) or a radar display, such as air traffic controllers use.  Each person within range is visualized as a colored light or dot, with the different colors of lights representing different species/subspecies, such as angel, demon, supernatural human, etc.  By focusing on a particular dot, she can instinctively feel how far away that person is from her.

What are the limits?
Currently, Luka's maximum range is about 600 feet (roughly 1.5 city blocks) in all directions (including up/down) if she is concentrating really hard. However, she can generally only sense a few hundred people at one time, so if there are a lot of people in the area she is in her range will naturally decrease. Her range is also dependent on concentration, so if she's not concentrating particularly hard or if she is interrupted, her range will be less than her maximum. 

Luka can also only sense people, her riftpower gives her no knowledge of geography or anything like that.  Additionally, she can only sense the presence of people.  Mindfeeling gives her absolutely no information about what anybody is thinking or feeling.  She cannot learn information about people's names, ages, gender, sex, nationality, etc. through mindfeeling.  She can only tell location, distance, and species, and even with species she must talk to a member of that species and learn what they are called before she can associate the name of a species with their mindfeeling color.  (i.e.  Luka now knows that blue means angels, but before she actually met an angel and asked them what they were she only knew that some mindfeelings were blue.)

Can Luka find specific people using mindfeeling?
Yes and no.  Generally Luka can only do this if the person she is looking for has a one-of-a-kind mindfeeling (Babel, for example).  All members of a specific species feel alike to her, so she cannot tell the difference between, say, Phoebe and Elizabeth, or any other random angel for that matter.  Also even if someone does have a OOAK mindfeeling, if they are significantly out of range Luka will not be able to feel them.  If Luka is at Grant Park and Babel is at the Main Gauche, Luka will not be able to know where Babel is.

As Luka's powers develop she might be able to differentiate mindfeelings of the people she interacts with the most, but this is something she's going to have to work up to and it will take a while for her to discover, if she discovers it at all.

What are the colors?

Riftverse native  Dot type: • (circular)
Angel -- bright blue
Demon -- bright red
Human (regular) -- light gray
Human (supernatural) -- white
Vampire -- dark blood red

Wanderer Dot type: ♦ (diamond)
Angel of the Lord (Castiel)  - dark blue
Babel -- bright pink
Cats, Talking (Cy, Ragnar) -- purple
Duo (Dev/Ace) -- gray-green
Fallen Angel (Flauros) -- dark green
Fae (Aurora) -- brown
Human -- white
Iris Fortner-- amber
Rat (Saul) -- army green
Species (Arlin) -- tan/sepia
TARDIS (!TARDIS) -- rainbow
001 (040798-332) -- dark gray

If you play a character of a different species that is not listed here, feel free to pick a color and comment to this post to claim it. Keep in mind that subspecies of human that are significantly different than normal humans will register as different species (e.g. mutants, Jack Harkness, wizards, etc.) and will also need to pick a color. Additionally, things that are called the same thing but but hail from different worlds may also have different colors (e.g. Supernatural-style Angels of the Lord vs. Riftverse angels), if they so choose. Also keep in mind that people who play characters of the same (sub)species are represented by the same color, so you might want to talk to other characters who play the same species as you. (As of the time of the writing of this post, that includes HPverse wizards and Time Lords.)

Any more questions? Feel free to ask here or hit me up on AIM (dragonsrule637).

[Luka's handwriting appears to have regressed quite a bit here. It's shaky and barely legible.]

dont like

dont like               hospitals




scary




want aaron           miss him

want to go to russia but CANT

Title: Without You
Rating: PG
Words:613
Characters: Luka Petrovic, mentions of Arlin Keysa (kineticmachine) and Duncan (greasethewheels)
Summary: Luka has trouble sleeping at night.
A/N: Written for throughworlds and varymydays using the prompts “This hole in my heart is in the shape of you and no one else can fit it. Why would I want them to?” and “Without him, the world around me changes. The trees are bare and everywhere the streets are full of strangers." Also used is 30_losses prompt #20A - "In the dead of the night." This story has all the prompts, yo.

( When he left, she started prowling the streets at night again, looking for fights. )

Dear Aaron,

There's been a lot of things happening here lately.  First last week a bunch of people disappeared, and then on Friday a giant rift opened up and destroyed the Conrad Hotel.  There was lots of monsters coming out for a long time.  I helped dig people out and shot monsters when they got too close.

What is Moscow like?

From,

Luka

[If you think your character should see this entry, they probably can. This DEFINITELY includes Babel, J, Phoebe, & Elizabeth.]

Is everybody all right?

If one of your friends is sad because someone they loved died, what is a good way to make them feel better?

[locked to J, Babel, Phoebe, Indy]

Meet at:
Athena
212 South Halsted Street

Saturday @ 6 PM

[locked to J]
Remember how I asked if we could go out to dinner sometime?  Work's been busy, but I have time now.  What kind of food would you like to have?

[locked to Babel, Phoebe, and Indy]
I was going to go out to dinner with my friend J sometime soon.  Did any of you want to come as well?

[phone call to Arlin]

I bought a Christmas present for you.

[locked to Jason (J)]

I bought you a Christmas present.  Is there any way we can meet somewhere so I can give it to you?

[locked to Babel]

I bought you a Christmas present.