Ether War is a frenetic, hyperkinetic, pyrotechnic, almost epileptic whirlwind of a shooter. It's not a particularly complicated game, but it'll keep all of your senses quite busy.
You have a basic shooter setup -- WASD to move, mouse to shoot -- and your objective is to defend your space station from the enemy Brood Mother, which spawns all sorts of orb-shaped enemies to throw at you. Fortunately, your space station has weaponry of its own, and can also spawn allied ships to help you battle the Brood Mother. At the beginning of the game, you're primarily playing defense. But as you destroy enemies, you collect ether points, which allow you to upgrade your ship and your allies. Eventually, once you've gained enough power, you can start to take the fight back to the Brood Mother and eventually destroy her.
The game is very fast-paced; don't expect too much in the way of precision aiming, it's very much just spray and pray. You don't have any lives; rather, when you get destroyed, you're out of the action for ten seconds while your ship rebuilds. (Your ship is protected by a fast-recharging shield, so the only way to get destroyed is to take a large amount of damage in a short amount of time. This generally doesn't happen much, except when you're mounting the final assault on the Brood Mother, when it'll probably happen a bunch of times.) Because the action is so chaotic (although you can follow the general flow of things on the very useful radar display in the lower corner), it's often hard to tell how things are going. This is especially frustrating when you can't tell how your space station is doing -- the game will occasionally flash an alert when the station is taking heavy damage, but it's often hard to figure out exactly where and how much.
The graphics are very pyrotechnic. Any time an enemy (or friend, for that matter) is destroyed, it fills the area with a shower of brightly-colored sparkles, so although this is presumably set in space, it's actually quite bright most of the time. The bacgkround music is a pleasant techno which matches the feel of the game brightly, and it's long enough and unobtrusive enough that you won't get too sick of it. The sounds are pretty straightforward and add to the fireworks atmosphere of the game, as a ship blowing up sounds like of like fireworks going off.
Overall, Ether War is not a difficult game -- you might fail your first time through, but once you get the hang of it it's pretty easy to win -- but it's got enough action to keep you occupied throughout. It probably wouldn't fare too well if it were much longer, but as it is, it's just the right length to be a satisfying experience.