Axis is a retro-styled game a bit like Missile Command crossed with a graphing calcuator. Instead of pointing a turret and trying to estimate a parabolic trajectory ending at one of your enemies, your shot follows the path of any function $y=f(x)$ you can think of.
You’re only given a minute to write down your function, so breaking out pen and paper to calculate an interpolating polynomial is out – but using Wolfram|Alpha isn’t!
A little hint that isn’t completely obvious – the coordinate system for your shot is centred on the position you’re shooting from. Sometimes it’s a bit disappointing that your pieces can be placed such that there’s no clever way for your shot to get to the enemy, because its trajectory is strictly monotonic increasing in $x$. Maybe a version in polar coordinates would allow more clever trick shots.
Anyway, find a friend and give it a go. It runs in your browser, and you can set up a private game by sharing a link.
Play Axis online: axisthegame.com