Perhaps the most arcadey title on this list, Ultratron has retro-inspired graphics and a soundtrack to match. It’s a twitchy, arena-style, single-screen shooter where you control a small robot and have to collect coins from slain enemies. Upgrades and bonuses are available between battles which are absolutely necessary if you have any hopes of surviving. The highlight are the bosses, which are guaranteed to make you burst a blood vessel or two.
In the tradition set forth by games such as Braid and Prince of Persia, Zeit² features a “rewind” mechanic affording players the ability to reverse time. This is especially useful since dispatching numerous enemies relies on creating a temporal duplicate of yourself and laying the smackdown on them with double firepower. Indeed, some enemies exist outside of spacetime and can only be defeated while time is moving in reverse. It’s a clever concept and requires more strategy most of the other games on this list.