If you ask me, sound design is such an underrated facet of a good puzzle game. Think of Game Boy Tetris and the wonderfully weird little squiggle it treated you with for clearing four lines at once. Or the original Puzz Loop's snooker-ball clacks, Bejewelled's clinking gems and Drop7's porcelain crack. It's a big part of what keeps you coming back - if you think about it, a lot of puzzle games are essentially about tidying up, and the pops, bangs or jingles that reward you for a job well done are the game equivalent of being handed a sheet of bubble wrap after hoovering the spare room.
Robot Invader understands this, and that's why Rise of the Blobs gives you the full works. You get a delightfully squishy sound for removing a lone blob from the field of play, but take four out and it's joined by an echoing string of pops. Six prompts the strum of a guitar, and eight grants you the thumping whack of a pool ball thundering into a pocket. All of the above are accompanied by gentle ascending arpeggios. In short, taking care of business in this sounds great.
Happily, its systems are also brilliantly tuned. Your job is to prevent a rising tide of gelatinous cubes from climbing a cylindrical platform to reach a sentient sweet called Marsh Mal. You spin the plinth with your finger as Mal takes aim with coloured fruit, swipe down to hurry its descent, and then tap to pop the fruit when it comes to rest inside the jelly. This then triggers a chain reaction, exploding all directly connected blobs of the same colour. It's a bit like poking a trifle to death.
The beauty of not having to pop straight away is that smart players can wait for more blobs to arrive rather than chipping away at groups of two and three. Or you can let fruit rest on the top layer of blobs, before triggering an explosion below, and letting it fall into the newly uncovered layer, giving you the chance to set off another satisfying chain of sounds.
Better still, this is the rare freemium game that is sensitively monetised. The coins you earn from a completed game can be spent on a variety of power-ups, like coconut bombs that eradicate every colour of the blob they land on, or hammers that swipe away the upper layers of any dangerous blob towers. Or you can invest in permanent perks, like rainbow fruits or TNT blobs that explode on impact. You'll only have to pay once for the perks, but you can spend coins to level them up, increasing their effectiveness or the frequency of their appearance.
You'll have to pay for more power-ups to replace the ones you've used, of course, but they're very fairly priced. In fact, it's almost too reasonable - most players will earn enough coins from a single game to stock up on power-ups and because they increase your chances of a better score, you'll be able to afford even more. In real money terms, I ended up paying out just £2.49 for a VIP pack (which unlocks one more game mode and a couple of level skins) purely because I'd enjoyed the game, which is as it should be.
The only misgivings I have are with the speed of the game, which increases too quickly - though the controls are responsive, it can get a little fiddly as the pace accelerates. And it's hard to keep an eye on the entire cylinder; you might focus your attention on one stack of blobs only to miss the fact that there's a taller tower on the blind side. It's your job to keep tabs on such emergencies, of course, but Mal hurls the fruit down at such a rate that he's as much of a problem as the blobs themselves. And the music, in sharp contrast to the excellent sound effects, is entirely forgettable.
Otherwise this is a fine piece of work - well presented, packed with unlockables and incredibly moreish. Most importantly, it's a freemium game that doesn't force you to spend to get anywhere. And that, along with all those satisfying squelches, chimes and pops, will be music to anyone's ears.
8 / 10