That's the sort of game that should have an exclamation mark. Robokill: Titan Prime to give it its full name. It's a browser embedded (although does some Flash downloady gubbins) from Rock Solid Arcade. Top-down, mouse/keyboard arcade excellence.
It truly is excellent. There's RPGish bits and bobs, with an inventory for weapon and shield drops, and a limited number of slots in which they can be placed on your mechanical friend. There's a shop on each level at which the unwanted is sold, and the wanted is bought. And you level as you progress, improving your basic skills enough to keep up with the increase in enemy difficulty. But this is really all about frenzied gliding around the room, running rings around the influx of enemy robots, and doing your best to not fall off the edges.
It's incredibly satisfying to get better at this, realising techniques for particular baddie bots, making intelligent use of cover (especially if you've got a laser equipped to shoot over it), and never, ever not moving. In fact, things can get to a Geometry Wars level of intense as you're encircling a room, dodging not only dozens of enemies (running into them is the most lethal mistake other than falling off a ledge), but also the gazillions of bullets and energy blasts filling the screen.
The design is not perfect. The biggest mistake is the difficulty spiking. Each level consists of a collection of interconnected rooms, often with multiple routes to pick to reach goals. However, a room early in a level can be hair-pullingly hard, then followed by a series of areas you fly through without thinking. As much as I loathe all forms of boss fight, having things get more tricky as you near the level's goal would make more sense. Also, many rooms can quickly feel repetitive, some using the very same layout as the previous.
What is pretty perfect however is the death debt. Each time your robot clogpops, you're not only financially fined, but the opposing robots reclaim two of the rooms you'd previous cleared. These aren't necessarily rooms you need to be cleared, or they might entirely hinder your progress. When things start going wrong, you can make some hefty backward progress, but in such a way that it feels deserved. And your robot's ability to teleport into rooms equipped with a portal means you can often happily sacrifice the gaps. Often you'll end up clearing unnecessary rooms just so they might get reclaimed, rather than more important ones once you reach a tricky section.
As should always be the case in this sort of game, the different enemy types start to take on a pseudo-personality in your head, such that some you come to feel fond of, and others you'd immediately punch in the face if you met them at a party. A space robot party.
The first third of the game is entirely free, and a good number of hours. The second two thirds will only cost you a measly $9.95 (about £5), and it's well worth it. I've spent huge chunks of yesterday and today with this, and am currently struggling with the final level.
Thanks to Simon for yet another top tip.