Aqua is a light competitive two-player card game designed by Ta-Te Wu and published by Sunrise Tornado. It uses just 18 cards so it qualifies as a micro game but it's quite unlike most other 18-card micro games. Aqua is a set collection game where the cards all show aquatic-themed paintings and the players represent curators in an art gallery. The curators don't see eye to eye, however; one is focused on vertical alignment and the other on horizontal...
This means that in this game both players will be placing cards out in a grid but one player will be scoring for columns and the other for rows. Players take turns placing out a card from their hand of three. The card they play must be orthogonally adjacent to a card already in the grid. If they lay next to a face-down card then they lay their card face up, and vice versa. The orthogonally adjacent cards are all then flipped. That makes this also a memory game: you need to keep careful track of what's where because at the end of the game all the cards are flipped to their face-up side and your rows or columns will only count towards your scoring if the total value of all the cards in a row/column is in the 10-20 range.
The 10-20 range isn't what your row/column scores, however. You will actually score for sets of matching numbers and icons, and for sea turtles adjacent to wave cards. There's more: whenever a boat card is placed out, two 'visitor tokens' are added and one is repositioned by each player. These add a point when the card they are on scores. Finally, there's a bonus to be earned for each adjacent row or column with at least one lily pad card.
Tho' gameplay is simple, there's quite a lot to keep track of in order to optimise your own score and minimise the score of your opponent. But even if you've a faltering memory and struggle to keep track of what those face-down cards show, there's always Ta-Te Wu's art to admire. And this is a game that plays comfortably in 15 minutes so Aqua is never going to overstay its welcome.