Bloons TD 6+

Chaotic, brightly coloured, and with an immense profusion of power-ups, heroes and abilities, which are gradually unlocked through a series of different levels and one-off events, it’s a long term challenge that’s extremely moreish right from the start. The upgrade path means you’ll slowly start to take on higher difficulties as you gather more monkey towers to your cause, making for a compelling difficulty curve in this near-perfect genre exemplar.