Some genres are so saturated with class, and so large in the first place, that a new contender needs something special. A name as unimaginative as Jelly Defense doesn't help. Although, to be fair to its developers, the bleed of SEO tactics into the App Store's line-up makes such blandness almost a pre-requisite for success. What's that thing about judging a book by its cover?
Jelly Defense makes a good first impression by virtue of its gorgeously gloopy world - looping monochrome backgrounds dotted with bright, bouncy jellies and skittering enemies. It serves a purpose, too, as the key twist to the usual tower defence ruleset is in the form of colour-coded enemies. Red towers attack red enemies, blue towers attack blue enemies, and certain towers are half-and-half. Which sounds manageable, but is the reason behind almost every restart and failed level. It can hurt bad.
The goo-goo eyes and cute touches are there to distract attention from the fact that Jelly Defense is a monster. Things start off simply enough with a few levels featuring long curves and plenty of time to bosh the clueless jellies. Perhaps a little bit of over-confidence settles in - who knows? Then things turn ugly. Jelly Defense has balls of pure steel, and intends to take a hammer and test yours.
This is tower defence on a knife-edge. One example of how Jelly Defense does things is its coins - the resources you gather from defeated enemies in order to build more towers or upgrade. Tapping on the coins to bank them is a straight lift from Plants vs. Zombies, but PopCap's game is much more forgiving of distracted players: the sundrops sit around for ages. In Jelly Defense every single coin is a crucial one, and missing more than a couple can seriously impact your game. So, of course, the coins disappear a few seconds after appearing - with just the tiniest of flickers before vanishing forever.
Placing such demands on players is risky, but it's bracing too, especially given the genre's tendency towards cakewalks. Jelly Defense succeeds because the towers and enemies work in crossover with unexpected combinations, and its environments are weird and multi-faceted enough to constantly freshen up the tactics.
In each stage there are 20 crystals to defend from incoming jellies, which stream in from multiple entry points. It's a bit weird to use military lingo about something that looks like it should be on Cbeebies, but trust me on this. The paths the jellies take to the crystals are windy and often long - and, even if they grab one, there's still a chance for a last-ditch zapper tower to make a saving shot.
There are always obvious chokes or dangerous shortcuts, and building is an ongoing process as levels unfold. Each stage begins with an ideal strategy which has to be kept going alongside the give-and-take of what the jellies are actually doing - if you blow all the cash on red damage, Jelly Defense has a real knack of sending in blue speedsters (hedgehogs, which somehow makes them more loathsome).
The thing about tower defence games is that there's so many, and almost everyone's played one. Lots of us are good at them through simple familiarity. Jelly Defense is a winner because it demands you learn how its system differs, and then work for victory in almost every stage. The pace quickens, recedes, then quickens again - and upgrading at just the right time to smash back an incoming wave is beautiful. It may not sound like it, but Jelly Defense is stout, unyielding - and, okay, quite sweet.
App of the Day highlights interesting games we're playing on the Android, iPad, iPhone and Windows Phone 7 mobile platforms, including post-release updates. If you want to see a particular app featured, drop us a line or suggest it in the comments.