Cold likes to play his game of being simple. He's just a criminal and he loves what he does. There's nothing more to it. That he doesn't care about anyone or anything (with the exception of Lisa, his sister). 

We find out through the show that's not really true. Well, even that isn't 100% and if I've learned anything about Captain Cold is he's a lot more complicated than what anyone knows. To the point that the various layers of ice that is his personality are not very easy to put into words.

For the most part he closes himself off and doesn't allow himself to give a shit about other people; that would cause problems. That's not to say he doesn't care at all. Even in his work he still plans things out so the job gets done quick and efficiently without casualties. The moment things start to go pear shaped and out of his control he's not afraid to back out and count it as a loss and try again some other day even if they leave empty handed. He's very strategic and calculating. That isn't to say he won't push the envelope ever but he's not brash and stupid enough to stick around when it isn't worth his time. If someone gets injured its on them and if it came down to it he would leave someone behind if he had to (though I can't imagine he'd do that to Lisa, ever), but allies and cohorts are hard to come by and they tend to work more efficiently when they believe you won't just abandon them to save yourself. Snart will do what he can to get everyone out safe and alive, but he also won't hesitate to do what he needs to do.

Of course, stand in his way, prove yourself more a problem than a help with his plans and he's not afraid to put you out of the picture. Permanently if he has to, if only to protect himself. And everything he does is to do just that. He's very good at looking out for number 1 (though with his sister back in the picture number 2 is priority as well) All of this probably comes from his upbringing and working with his father. Cold is very strict with his rules and working with him is probably no cake walk, but do just as he says as precise as he wants it done and you'll do just fine. A few kinks in his plans don't deter him however, he's a quick thinker and able to find other routes or ways to adjust to the situation. It's very rare that he loses a cool head or reacts strongly to anything. It isn't until after a botch job that you might see a more dangerous, terrifying edge as he utterly rips you a new one for screwing something up. It's a flash in the pan usually, and before long he'll reign himself in and give you that familiar cold shoulder.

At the beginning of the Flash he killed easily and it's not until his run in later with the Flash that he agrees to stop needlessly killing people or hurting innocents. And despite everything he has stayed loyal to that promise. It's part of what kept the Flash off his heels and allowed Cold to remain free instead of behind bars. But more importantly it was Barry's words that made him loyal to the promise. Pointing out that he doesn't need to kill to prove he's good at what he does. It's one time they managed to see eye to eye, that the other managed to get through to him enough that he agreed. So he won't kill just to prove he's better than that.

All of that changes when Barry helps Len to save his sister Lisa and it's during this episode we start to see a little more into Leonards character outside the diamond stealing criminal. Captain Cold shows a moment of compassion when he thinks his father has shot the kid, even going so far as to utter an apology. He looks somewhat hurt and sympathetic, a rare moment of emotion on his face. In the end it proves not to be true and despite angling his weapon on Barry he hesitates to kill him. Even with his father yelling in his ear to do it. He stalls long enough for Cisco to remove a bomb implanted in his sisters neck (which his father was using as a way to control Cold). Then and only then he kills someone and breaks his promise to Barry. He finally gets closure by killing his father and almost willingly gives himself up to be taken into custody. Barry is even able to take the cold gun from his hands without any sort of struggle. Perhaps there's some remorse or mourning for how things used to be, back before his Father became so desperate and twisted that he'd hurt his children and force them into a life of crime to survive. Guilt for having to do what he felt was necessary even if it hurt him. He'll deny it and say with a cold expression that he's glad the man is dead or that he had it coming to him, but he still misses how things could've been if their lives hadn't gone so wrong.

I can imagine a lot of his emotional conditioning has a lot to do with his abusive father. Emotions were probably driven into him as being a weakness. He wasn't allowed to show fear, he had to become cold and calculating. He had to be the perfect criminal to keep his dad happy. Everything had to be precise and perfect. But suffice to say nothing was ever good enough for that man so he had to get better still. And to this day he strives to be better than he ever was. He doesn't want to be anything like his father even if there is a part of him that knows he has become just like him in ways. And he hates it, but its who he is and he does what he can to be better still.

Lisa is a major thing in his life--probably the only major thing in his life--he raised her pretty much on his own and did everything he could to protect her from their abusive dick of a father. Leonard did what he could to attract his father's attention when he was in his moods, to keep Lisa from being hurt, but even then it wasn't always enough. He looks out for her and after her and because she is family she is the only one who knows who Leonard really is. And she also understands her brothers need to not show that side of himself to anyone. She may vouch for him on occasion but she won't go against his wishes.

From the start he never mentions his family, he only touches on the subject when he introduces his sister. He doesn't outwardly show affection towards her or speak much about her. He plays a lot of things close to the chest and just because he hides behind a mask of ice, doesn't mean he doesn't care. The less people think or know things about him the better. The easier it is to keep them guessing. It's to protect himself, but more importantly it was to protect Lisa. To anyone on the outside looking in he won't show much to them for the sake of seeming cold and distant. It's easier this way if they believe he's disconnected. Especially for any enemies he might have so they don't try to use Lisa against him or harm her.

He doesn't want people like Barry Allen to figure him out, that's when his guise starts to fall apart and when people start trying. He doesn't want to be saved and he doesn't want to let anyone in or let anyone close. He's been guarded his whole life and its what makes him feel safe and strong. The walls are up because it's how he's had to live and how he knows how to survive. It's the life his father forced him to live and it's something he became very good at. It's something he grew to learn to love and want to be the best at. He enjoys the challenge and the thrill, that excitement of a heist and to not get caught. Danger, to a calculated degree, is always something he will flirt with. 

All in all Leonard is living the only way he knows how, but it's something he came to own. It's who he is. It's what's made him strong. It's why he won't just give it up and change so easily like Barry wants him to. He's enjoying it too much and in a way he's become somewhat obsessed with the one thing he can't defeat. Barry Allen. The Flash. His nemesis and rival. Even as a normal human he can combat the Flash stride for stride and still somehow slip out of his fingers. And yet we see him time and again baiting the Flash because he wants to test the limits, see if he can beat him and when he knows he can't, prove he can escape it and still remain free. There is probably a part of him that wants to get caught, that wants to stop, a part of himself that he won't recognize or listen to. He enjoys his freedom too much and the power it brings to tango with the fastest man on earth and still get away. To be able to do whatever he wants, whenever he wants and to get all that he wants because he can. But he's not in it for the money, or for any love of the things he steals. He goes for the biggest and the most challenging items just to prove he can do it. It's for the notoriety. He enjoys being infamous. It proves he doesn't have to be a metahuman to be powerful.

There's something liberating in chaos to him, which is why he tempts fate so often. That chance, even if it's slim, of being caught is enticing to him. He's had to live with strict rules or suffer consequences, his fathers law controlled him, he's had to keep such a tight hold on everything that in that moment when it all starts to unravel he feels most alive. So like a drug he seeks it over and over again. And he comes out on top every time and it's freeing. And when he faces the Flash? That risk is ten fold. He's the one man in Central City that could best him. There's power in the control he wields, to be able to predict and bait the hero to him only to out smart him and escape. And yet, that lack of control is addictive too.


Captain Cold vs. Leonard Snart - He owns the captain cold persona, putting forth the face of the criminal as being just who he is. But Lisa and Barry have started to see the man that is Leonard Snart. And Leonard is the humanity that he hasn't lost. He separates himself whether he realizes it or not. Don the glasses and the coat and he's Captain Cold, but under all that he's just Leonard Snart. A kid growing up in a bad situation without a good influence or any love and affection in his life. He's had to grow up fast and grow up strong not only for himself but his little sister so that they could survive and one day get away from their father and live their own life, a better life and to be free. But doing that certainly took it's toll and had it's price but Lenny did all that he could and all that he knew how. He is a good man and a good brother, despite all the bad that he does and the people he hurts for selfish reasons. He probably wouldn't be so redeemable if it weren't for his sister. If he didn't have her to keep his feet on the ground and his focus sharp on whats important, he may not be the man he is. He's no hero, he's definitely trouble, but he's still got a good heart and hasn't been lost entirely. This is the part of him that Barry sees and clings to steadily in hopes he can one day change Leonard for the better and show him he doesn't have to be a guarded criminal anymore. That he can do something good and make a difference and be happier living a normal life.

 

ties to the city?

Len has the moves - but even then he'll pick pocket a lady after sweeping off her feet. Why? Because he can and perhaps because it diverts anyone who sees this other side of him. He wants people to expect him to be selfish, to keep seeing him as a criminal and he likes to show off. He's no hero and he's driving that point home. He may be suave and slick when he wants to be, doing better than the boy scout with his innocent charms, but he misdirects with the slight of hand so it keeps others firmly routed in the idea he's just a petty thief.  (Will add more here)

Dad goes from decent father/half-baked thief to abusive jerk and dangerous criminal - effects on Leo/Len

Abuse has caused him to become guarded because the person he loved, looked up to, trusted and followed, his own father hurt him. He's become closed off because it's how he's learned to survive. When he's hurt he draws inward, distances himself to protect himself, preferring not to feel or let things affect him, staying strong no matter what. When he feels something genuine for someone he pulls away, rarely allowing himself attachments. When he does allow someone in he becomes fiercely protective of it but also keeps himself guarded where he can because of that subconscious fear of being hurt by them. He keeps everyone at a certain distance in the event they will betray him, turn on him, leave him or hurt him and he has to protect himself. He believes won't let anyone hurt him, but sometimes the heart is more complicated than that and sometimes he ends up hurting anyway. Not that he'll allow anyone near him when it does happen or ever let it really show, denying it when those closest to him take notice. Choosing to close himself off and wallow alone to lick his wounds in silence, dealing with it on his own, as he always has or always had to. He's not used to having someone there for him when he needs it. Mick was a good partner, but they never really talked about their feelings, Len had to be strong for Lisa more often than not and he didn't want her to ever see him weak. He felt he needed to be strong and seem fine through everything for her sake. He was her rock. As they got older there may have been a time or two lisa saw through his mask, but he would've been reluctant to break in front of her, too proud to appear weak for the one person he always wanted to be strong for.

 becoming a criminal to help his father in hopes he'd stay? be happier? Not get arrested again?

Mick and how important his partner is to him/his loyalties