This game is an unlicensed version of Joust.
From the inlay:
Astride your thoroughbred Ostringo, you, Herbert of Hardingham must Joust with the Knights of your evil twin brother Sir Howard for the hand of your fair Lady Tess.
Skirmish is a clone of the arcade classic Joust, written by Delos D. Harriman and originally published by Godax for the BBC Micro and Acorn Electron.
The game is set on a single screen with several platforms. The screen wraps around so if the player or an enemy exits one side of the screen, they reappear on the other. At the bottom is a fiery pit of lava covered by two bridges (these get burned away in later levels creating an additional hazard for the player).
Pads on the platforms spawn knights sitting astride flying ostrich-like birds. The player controls one of these knights and can control movement with left, right and flap keys. Repeatedly pressing the flap key causes the mount to fly higher. Each knight carries a lance and when two collide, the lower-flying knight is killed. For the player, this results in the loss of a life. When enemies are killed their mount drops an egg. Eggs need to be collected, partly to collect points, but also because if the egg is left too long, it hatches into a new knight which is picked up by a replacement mount ready to re-enter the fray. Killing all the enemy knights on a level allows the player to advance to the next stage.
Each stage has slightly different rules, which include survival waves, where the player earns bonus points for not losing a life during the stage, egg waves, where the enemy knights do not start on their mounts, and others.
Each stage has a time limit. At the time limit, an "unbeatable" Pterodactyl enters the screen who kills the player on contact. The player must kill all the remaining enemies on-screen before being killed by the Pterodactyl.
In the two player game, both players are on-screen at the same time. Some levels are cooperative, others are competitive, where additional points are scored for not killing or killing your fellow player respectively.