For newcomers, Lock's Quest is a solid tower defense/strategy/RPG/action game that should merit your attention. If the old school aesthetic doesn't appeal then well, it's all over this game so you may not have the wherewithal to dig and see what else this game has to offer. At times it's tough as balls and will certainly test your skills, however the lengthy campaign ensures you get enough bang here for your buck.
It's a monumental pain in the ass at times and is perhaps too much of an onslaught for the less experienced in the genre (our advice is to start out on rookie. You'd be surprised how big of a leap it is to 'experienced'), but for those who are after a game where you can take on the world in a variety of modes (MUST. COMPLETE. FEATS. BOARD.), there's no reason at all why Nex Machina shouldn't be the top of your list.
Obviously you'll need to either already enjoy playing Chess or have a desire to learn the game to want to play Chess Ultra in the first place – giving the game a relatively narrow appeal – but this is a beautifully designed game that Chess novices and experts alike could quite easily lose hours and hours to, and at just £10 it is incredible value for money.