You don't need to have an economics degree from Harvard to know there are tried and tested methods of flogging even more units of an ageing game – selling it cheap, including it in a retro compilation or perhaps taking inspiration from the supermarkets and offering two for the price of one.
The latter, it turns out, is what RealArcade has decided on for a couple of its classic puzzle games previously released on mobile, Gem Drop and PileUp! And we're delighted, in a way not too dissimilar to our pleasure at walking into our local Sainsbury's and finding the store is doing a 'two-for-one' on products we were actually going to buy anyway.
That's because both puzzle games – particularly PileUp! – are quality items, so you'd already be happy with just the one. With two, well, let's just say no train, plane or bus journey need ever be dull again.
Not unlike Anne Robinson, then, we'll begin by weeding out the 'weaker' link, Gem Drop. You might be familiar with this, a game with the most literal of titles seeing as it simply consists of dropping gems. There have been free versions available to download online for a while, although most aren't as polished as this.
It's probably fair to assume Gem Drop's concept didn't take 100 men, 100 hours to think up. Not only does it use the age-old puzzle game formula of arranging falling objects into like-coloured groups to make them disappear, it also doesn't add a lot more to that concept.
Single gems of varying shapes and colours line up at the top of the screen and, one by one, must be dropped onto the stack below. You can swap the current gem in line for the following one, but apart from that there's nothing else to do other than move it left or right, then drop it in the most suitable of six columns.
Linger on a gem for longer than a few seconds and it wobbles before falling, meaning you're forced to act fast. Like the DS game, Zoo Keeper, the skill lies in being able to scan the rows of gems to quickly determine what should go where.
Bundle three of the same gems together and they vanish, leaving the precious stones they were supporting to drop down. Matching three gets you points, of course, but triggering a cascade – that's when matching one group of gems causes another group of like-coloured gems to fall into place, subsequently disappear and so on – earns you bonus points.
There are a couple of variations on the norm, too, such as when one of two special gems appears in your line-up. The pickaxe gem, for instance, clears all the gems beneath it (except white diamonds, which are the most valuable and indestructible of the game's stones), while the black gem clears the screen of all the gems identical to the one it lands on.
It's all very basic stuff, although fairly addictive. And let's not forget, Gem Drop is actually the more disappointing (relatively speaking) of the two offerings here.
As such, PileUp! shines brighter and will undoubtedly keep you playing for longer. Ultimately, it's the game that offers more originality, skill and variation on each level.
At first glimpse, it's like a cross between Tetris and that Sony Bravia advert with thousands of balls bouncing down the street. Clusters of three brightly coloured spheres appear at the top of the screen and need rotating to match up to four or more of the same colour.
Do this and, you probably won't be shocked to learn, the balls disappear. However, when they do, a mini-avalanche is triggered, with gravity shifting and sliding balls into new positions. As in Gem Drop, point-boosting cascades can occur, but here these prove far more satisfying and frequent.
Every level has a different objective – it might be to clear 80 balls, to empty the game area or to score as many points as possible in 30 seconds. Each stage also begins with a different formation of balls already in place, carefully organised into precarious pyramids reminiscent of a big pile of multicoloured Ferrero Rochers you're just gagging to knock over.
There's certainly great satisfaction in sending 200 balls into disarray. And even more so if you can figure out how to cause a big enough chain reaction to get rid of them all with a single, carefully placed bundle of spheres.
So, these games might be old, but then the finest puzzle games never age. Okay, we wouldn't quite put Gem Drop up there with the very finest – it's a very simple puzzle game relying on a popular mechanic, though it is satisfying (even if a control flaw means if you press down to drop a gem just when it was going to drop anyway, the next gem drops instead – usually in the wrong place).
But with PileUp! present as well, the two represent an extremely decent puzzling bundle – one that leads to infinitely more hours' worth of entertainment than your typical two-for-one deal consisting of, say, toothpaste or pasta sauce.