How big is your brain? Testing your mental prowess is nothing new in gaming, given that legions of Nintendo DS owners have already consulted a pixellated Professor Kawashima to calculate their cranial capacity, but in an era of global leaderboards and Achievements, even on handheld devices, the ability to simply do something is now only part of the fun.
That's where Quiz Climber Rivals comes in, posing up to 50 general-knowledge questions with machine-gun fire rapidity. It's your job to pick the correct answer from a choice of four. Get the question right and your character, a blue squirrel thing, bounds up a branch on the Quiz Climber Rivals tree. Get a question wrong and it's game over. Players are bound to a 15-second time limit and the questions get harder the higher you climb. It's a test of quick-thinking and reflexes - there's certainly no time to search Google or (if you are somewhere no one can see you) ask Siri.
The four possible answers often begin as humorous riffs on a theme. For example, when asked the name of a famous Christmas bird, you'll be asked to decide between Riddler, Batman, Joker and Robin for the answer. But things get tougher fast, and topics cover everything from science and sport to popular culture.
Yes, it is a quiz app. And yes, it's largely the same quiz app as the original Quiz Climber, which we reviewed last year. But we've kept on playing it since then to an obsessive extent, because the real joy comes in seeing your friends' squirrels sat on their high-score branches and then leaping past. That sensation is something that the Rivals update - introduced after developer Relentless broke off from original publisher Chillingo - only enhances.
Rivals rolled out late last year and replaces the original Quiz Climber app entirely. It now encourages players to return each week to see how their scores match up to their Game Center friends as well as their Facebook acquaintances. Every seven days is a new mini-tournament for leaderboard superiority among your friends list and across the globe before scores are wiped clean and you're forced to have another go. How fast you answer a question is also taken into account, and your leaderboard position shows your average time alongside your final question total.
Revisiting the app is never a chore, as Relentless continues to update the game with new questions. After playing a couple of times a day every day for a couple of weeks I encountered just one repeat, along with a good few topical questions that demonstrate the frequency of updates.
Quiz Climber Rivals remains free and ad-funded, but you can buy in-game lifelines to revive your squirrel once should you mistakenly decide that Batman is a famous Christmas bird. 20 lifelines are 69p, 100 are £1.99 and 1000 are £18.99, but you can also earn lifelines naturally in-game through repeat play, and you unlock them faster if more of your friends are playing, encouraging you to spread the word and line up more opponents.
How big is your brain? That's not what Quiz Climber is really about, although I suppose you can have a stab at calculating it by interpreting the vague squirrel-worn branches of its towering virtual tree. But how smart am I compared to my friends? That's a question we keep coming back to answer, day after day, week after week, with no end in sight.