At first, Causality feels like ChuChu Rocket! with spacemen.

You get grid-based levels, and astronauts that automatically run until reaching a corner or hitting an arrow, whereupon they change direction. The aim is to help each to a destination square with the same colour as the stripe on their helmet.

But Causality has apparently got a bit obsessed with Doctor Who. Rather than just having you ‘pathfind’ your way to victory by fiddling with tiles and letting everything rip, this puzzler has you delve into time travel and teleportation.

At which point, it merrily smashes your brain out.

Time twister

Causality isn’t vicious enough to drop you right in it, though. Early levels have you master the basics, directing a single astronaut, occasionally having you deftly deal with directional and button tiles.

These early stages also get you manipulating time. You drag downwards to move forwards, and if an error is made (such as your spacemen being abruptly eaten by a tentacled monster), you drag upwards to rewind a bit and try something else. You can also tap the timeline at the foot of the screen to jump to a specific moment.

This is clever in itself, but you soon realise time travel in Causality isn’t just about fixing errors – it’s instrumental to progress. Before long, portals appear that fling astronauts through time, so they can work with their past selves to beat a level’s strict move limit.

Once you’re tracking several spacemen - some of which are in time loops - and antimatter shadows that obliterate any idiot daft enough to walk into them, it’s enough to make your head spin.

Wibbly wobbly timey wimey

Fortunately, Causality echoes hard-as-nails puzzler Snakebird in key ways that ensure you’ll want to continue rather than hurl your smartphone into orbit.

The aesthetics are first-rate. Stills don’t do the game justice, because you need to see the fluid animation, backgrounds that subtly evolve over time, and the VHS-style effects when you time-shift. The soundtrack is great, too – all punchy sci-fi bleeps and clicks, along with burbling background atmospherics.

Most importantly, Causality doesn’t leave you stranded on a single level if you get stuck. There are always at least two to tackle. Defeat ten within a 15-level set and the rest unlock – as does the first of the next set.

That’s not to say Causality won’t cause your brain to melt; it does, though, give you a fighting chance of reaching the end without having your own time-travelling clone from the future tell you how a particularly tricky bit is done.

Causality is available for Android and iOS. A version is also available for PC/Mac on Steam.

Stuff says... 

App of the week: Causality review

A clever puzzler with deviously designed challenges and a brilliant brain-bending time-travel device
Good Stuff 
Intriguing time-travel concept
Really smartly conceived puzzles
Designed for experimentation
Bad Stuff 
Some of the more complex level set-ups can seriously confuse