Gravi-o-roids!

“Gravi-o-roids!” is a new old-school game, a recombination of elements of the most classic space shooter games.

Control your own spaceship in outer space.
Stay clear of asteroids and their gravity fields.
Asteroids cannot be destroyed.
Destroy enemy saucers.
Outscore saucers to advance to the next level.
As with old arcade games, a level lasts for a fixed period of time. Time remaining as well as current scores and their balance are displayed at the top of the screen.
However, there is a price to endurance: you'll take just the half of the balance to the next level, the rest goes for maintenance.
Guide your shots by turning your spaceship.
This feature may be disabled in the game options, found below the screen.
Disable the gravity map, if your computer runs low on resources.

Mastering the Gravity Challenge
Thrust to vector perpendicularly to any asteroids in order to orbit around them. Steer right through the middle of multiple asteroids, where gravitational fields cancel out, rather than attempting to avoid such a group of asteroids.
Have a look at the gravity map on the top right of the screen to get an idea of how gravity affects your ship.

“Gravi-o-roids!” inhertits the following features

From Spacewar! (1962), the very first video game for a digital computer, the basic mechanics and gravity, which is here excerted by the individual asteroids.
From Computer Space (1971), the very first arcade video game, time-based levels, guided shots, and the mechanics of the saucer opponents.
From Asteroids (1979), the first successful single-player arcade version of a Spacewar!-like game, — well — the asteroids. However, in Gravi-o-roids they cannot be destroyed and excert a gravitational force on the spaceship.
The soundscape is generally based on Computer Space.

For a similar game, which combines these elements for a “Spacewar! trainer” or “Spacewar!-for-one”, see Outer Orbit.