The game-play is simple: slide a little water droplet around a window-pane, avoid the spikes and collect the pearls. Easy, right?

Absolutely, but the beauty of Quell is in the perfectly pitched difficulty curve - it's just taxing enough to test your powers of logic, but never so much so that it stops being fun. The gentle music (by acclaimed composer Steven Cravis) and ambience create the perfect setting to allow your brain to engage fully with these ingenious puzzles.

If you're willing to dig deeper still, there's a side narrative which tells a touching story of love, loss and nostalgia. Either way, Quell is a haunting experience that will stay with you long after you've finished it.