Timerun is a RISC OS implementation of a shoot-em-up game Tony orginally started in 1985 (where does the time go).
The game was released at the MUG fair, where it was being loudly demoed by its author! This is a RISC OS version of a classic 1980s sideways scrolling Arcade game, using the Amcog Games library. It has plenty of action, explosions and sound effects. There is a nice plot summary here if you need (I just enjoying jumping in and shooting things). It runs on most RISC OS systems (I tested it on RPCemu on my Mac) from keyboard and there is a joystick option. You can choose your starting level at the beginning.
If you miss the 1980s, it is much cheaper than a DeLorean and readily available from !Store or directly from Amcog for 9.99 pounds. An excellent addition to my collection!
There is a nice YouTube video if you to see more gameplay and I also grabbed some screenshots below.