My fascination with local multiplayer began out of accident. I was building the two-player mode for my iPad puzzle game, Greedy Bankers vs The World in 2011. To differentate the two players I split the game board in two, but forgot to put any kind of barrier between the sides. The result: players could reach across the board and steal from each other.

In fact, they enjoyed doing this so much I added a points bonus to every gem stolen this way, to encourage them to do it more often!

Pushing this kind of hugely social play has been a design goal of mine ever since, and was the driving force behind my next iOS game, Slamjet Stadium. The frequent physical contact between players meant there was constant personal interaction. The encouragement to invade each other's space made cheating okay. Most players ended up grabbing each other's arms out the way. Some even wrestled on the floor! Cheating in the physical space allowed unlimited creativity, and offered an opportunity for players to express the more devious sides of their personality. It was incredible to watch.

The experience was made possible by the iPad's 10-inch screen: large enough for two players to make meaningful gestural movements without feeling cramped. In 2014 there's a whole new range of tech that pushes these possibilities even further but - for now at least - it's been largely overlooked.

The large-scale touchscreen

Large-format touchscreens have been commercially available for the past year, fully supported by Windows 8. Since October I've been building a brand new party game on a 27-inch touchscreen All-in-One, and using a 23-inch touch monitor (connected via USB to a tablet) to demo it.

The game is called Tap Happy Sabotage, and is a culmination of the lessons I have learned from Greedy Bankers vs The World and Slamjet Stadium. You can get a feel for how it plays out in the trailer above.

There are two key benefits to having a touchscreen this large. First and foremost, you can fit considerably more players around the device. As a result, I made sure Tap Happy supports as many players as you can throw at it - technically up to 52 at once. 

Secondly, players get more space to move physically, and with more physicality comes more memorable moments and more fun for spectators. If Fingle is digital Twister for your fingers, then touch monitors enable digital Twister for the whole body.

From demoing the game at industry events I've been amazed by just how much energy you can get from four or more players. It only takes one person to start cheating for everyone else to follow suit. It only takes one moment of boistrousness for play to become a free-for-all, with all players setting aside notions of personal space in the name of fun.

Of course, a game that devolves into fisticuffs will not stay fun for long. Neither will a game sustain its momentum if smaller and weaker participants get barged out. Building Tap Happy has been a constant back-and-forth of public demos, lessons learned and revisions made. These are the lessons I hope to convey in this article.

Building a Big-Screen Party Game

The basic rules are as follows. Each player is assigned two picture cards. The first is your "target card" - tapping this in-game awards a player a point. The other is your "sabotage card" which offers the first opportunity for foul play - if anyone taps your sabotage card you'll lose all your points.

It's not uncommon for a winning player to see the rest of the players hunting down her sabotage card to keep her from victory! I try to make sure each round enables some kind of mean or underhand strategy, so that imaginative players can feel smart for spotting it.

Each round lasts roughly one to two minutes, with every second round being a major twist on play. In one round players must hold down three of their card at once to earn a point, creating an inevitable Twister-style bundle of arms. In another, a spiked ball bounces around the screen  and you must drag your card out of its path. Here players spot they can steal opponent's cards to fling into its way, or grab their friends' arms to stop them from dodging.

In designing these rounds the rules needed to be kept as simple as possbile, to make sure it was easy for new players to jump in and feel equally involved. Explaining each round in at most four words worked well, and those involving an action no more complex than "tap", "hold" or "drag" were most successful at maintaining flow.

Playtesting showed that it was important to keep this explanation visible at all times. Players usually talk to each other during down-time such as round intros, and won't always look at the screen until they hear the start whistle. 

In fact, the key skill in most rounds does not involve touching the screen at all. It's observation: the ability to pick out your card from a mash of similar-looking cards. That's a skill everyone can get, regardless of their age or experience with computer technology, and requires little explanation. This has made it easy to get a large group involved quickly, and is also a neat space-management tool. 

With so many arms play could swiftly become a stalemate if everyone's arms were always on-screen and no-one could see what was going on. By having frequent pauses in play, with the layout of the cards changing regularly, it forces players to take their hands off, giving everyone a view and a fresh shot at getting in.

All Hands on Deck!

Of course, between these convenient pauses, players' hands will be all over the screen; one of the design aims was to get every player using the full screen space. But with that in mind, it's important to take safety into consideration - you don't want players to feel like they're going to risk spraining a wrist! I'd learnt from previous games never to have a shared focal point in one place for too long.

An example of what I mean is in, Greedy Bankers vs The World. With the aforementioned stealing mechanic, every gem dragged from your opponent's side of the screen to your own doubled in value. So the most obvious way to protect your interests was to guard the centre of the screen. Unfortunately, some players would spend most of the game simply fighting each other over this one spot. If you added more competitors into this mix someone could easily get hurt.

In most rounds of Tap Happy Sabotage all cards will fall away after the first point is scored, so even if all the cards are in a localised spot they're not there for long enough to cause an issue. One round that required a lot of revision was the "Vote for the Winner" round, where the card that receives the most taps in five seconds gets a point.

In the early builds the cards would all be placed in centre-screen, but now they are evenly distributed across its breadth. While seven players furiously drumming on one part of the screen would be a recipe for injury, giving each player a different spot to reach for reduces the pressure on individual hands.

At demos I've made sure to keep an eye on which people get immersed and which people are reluctant. Fellow developer Alan Hazelden noticed at a recent demo that players would give up if they didn't score a point in the first couple of rounds. Since then the game's weighted so that anyone who's yet to score gets more of their cards on-screen. 

Just scoring that first point is enough for players to feel that they get the game and could be the champ, and are more likely to stick it out even if they're losing.

Hit the Road

Of course, with a game designed around obscure tech like this, how do you distribute it? I often get asked at demo events how many people own a touchscreen this size. The reality is that touch-based monitors and All-in-Ones are relatively niche at the time of writing.

I'm entirely confident that this will change in the years to come. After all, the touch interface is becoming cheaper and cheaper to add to hardware. It won't be long before it's added to monitors just because it can be, as is already the case with laptops.

Touch tables already exist and while they're an expensive luxury item right now, this is also likely to change as the technology gets cheaper. We might not be far from the return of the cocktail cabinet - arcade tables for pubs, clubs and bars. 

Even today there is huge potential for big-screen touch games in public spaces. Social play installations would be perfect at music festivals, for example, and big screens are already popping up in galleries, museums and libraries. It'll only take one forward-thinking local authority to use social play on their existing screens as a way for local communities to connect.

Lessons from big screens

Working on these devices has transformed my perspective as a developer. The design focus is less about creating an experience out of intertwining mechanics, and more about communicating with the player - engineering and encouraging the party spirit, and making a space for players to bring their personalities with them. It's an example of games as a springboard for players to interpret their own way, rather than a challenge for a player to master.

Of course, having seven players scream, shout and jostle over virtual playing cards on a great big screen is always going to be hilarious. I'm delighted to have found hardware that lends itself so well to social play and can't wait to push the technology even further.

Tap Happy Sabotage is available free from the Windows Store from this link, and will continue to appear at games events over the coming year.