Ouranos is a very classical shoot-them-up. It's endless, so you can play as long as you want. It's quite an old project, I started it in 2005. For the technical part, it's made in C++ with OpenGL and GLUT. I made the graphics with 3DStudio at that time
For the install, you have to download and unzip the compressed ZIP file. For windows, just launch "ouranos.exe" and for linux, "ouranos". You may have to install GLUT on linux.
Regarding the commands: use the mouse to move, left click for normal shoot and right click for bombs.