I don't really say casual or core anymore, I think it's quite hard to differentiate different things about games into those two categories since they're both on the very extremes of what someone or something can be and I don't think it's a good scale to work with because of that. What a few people have started to say, and what I do too which I hope starts to popularize soon to shut up people crying everything's casual now, is there are 3 different groups; Casual, Softcore, and Hardcore. And suddenly I think it's a lot easier to define exactly who is what and what game is what when you add in that third category, since it actually gives a middle-ground to the discussion. Instead of just being a Yes or No, there's a Maybe now. Instead of full or empty, there's half full/empty, depending on your disposition.
In terms of gamers themselves, I think the terms just concentrate on how involved a person is with the hobby. Not just how much time they put into it, a 'casual' gamer can play more hours on his phone than a hardcore gamer could, but moreso what they do in that time. Are they just matching coloured blocks on Candy Crush or are they playing Planescape Torment? Casual sort of speaks for itself, they're
casual about their hobby, they pick up the odd game or two and play on their phone and maybe have a console but they're not very involved in the goings-on of the industry or anything like that. Softcore gamers are the type who buy the new FIFA, Madden, or Call of Duty every year and tend to stick to just the big blockbuster titles. They love the games they play and are usually pretty involved in the games they play but aren't incredibly involved in the industry. Hardcore gamers are the most invested, they're the ones who check news sites everyday and watch E3 live and those sorts of things. They don't need to have a huge game collection or play for 7 hours straight, but, they're usually much more passionate about the industry. It's why they always argue.
To sort of put it in another way, think of those those 3 terms in regards to a sports fan! A hardcore gamer would be the type who buys the Season Pass every year, goes to see every game, can talk at length about the entire line-up of his team and more. Softcore gamers would be the ones who will buy a ticket every so often, whenever there's a Home game and friends are going, and enjoys the sport and knows the team but can live without not seeing them. And casual gamers would be the ones who just catch the scores on the TV or radio and know enough to hold a conversation but thats about it.
As for games, it gets harder. Do we gauge if a game is casual, softcore, or hardcore based on the audience they wanted to attract, or the audience that
does get attracted? They sometimes aren't the same, but in many cases they are. And similarly, like gamers, I regard the terms depending on the amount of involvement the player has in the game. A casual game doesn't have to just be a puzzle game, or even an easy game, but typically its very accessible, easy to pick up and easy to play, and tends to give a lot of gratification. Softcore games tend to have more depth than a casual game and take more time to master but are still designed to be accessible to everyone. Nintendo's games I think fall into this category more often than not; their games have a some depth and lots of content but ween you into it and don't go the full hog. A hardcore game can still be designed to be accessible to as many people as possible but typically has more depth than any other type of game, and requires a lot more time and involvement on behalf of the gamer. All types of games can be hard but hardcore games tend to be less forgiving with it, and then it goes down a peg each time. You wouldn't get Dark Souls levels of difficulty in a casual game, but later levels in many do pose quite the challenge.
To put it another way like I did above, I'd say we could compare videogames to boardgames. Hardcore games would be like the boardgame Risk; they've got a lot of depth and require a lot of effort on the player's part, it's not the type of thing that can be picked up instantly and isn't for everybody. Softcore games would be boardgames like Monopoly or Cluedo. Yes they have a lot of stuff going on and a lot of depth but it's all quite easy to understand, there's no huge complications to get in anybody's way playing it, and can be picked up quick after a little read through the rules. And casual games would be something like Frustration. You roll the dice and move that number of spots, and you need to make it all the way around. It's quick, simple, gratifying instantly, and very accessible. It doesn't have much depth but can still pose a challenge against certain people!
That's how I'd try and define them anyway.
It's hard to 100% nail down exactly what a game should be or should do to fit into each category, they typically just have to be looked at by their own merits. Everything is a factor and there's no real statistic stuff to say what's a hardcore game or what's a casual game. As I said in the paragraph above difficulty tends to be something people throw out but have you played some of the last levels on some puzzle games? Bloody difficult, is what they are. And I've played lots of games we'd assume are hardcore games but tend to be easy. It's why deciding what is and isn't hardcore, softcore, or casual requires very much situational standards. Looking at a game's target audience for a start is usually a good indicator or what exactly they are going for.
I think the important thing to note is, I consider all types of gamers equal!