I first played this on my friends BBC Micro B and loved it so this was a must for me the moment it was released on the C64.
The very colourful huge sprites and background made this a platform game like no other during this period of video games history.
Like most of the games of this era there was actually not many levels but the difficulty of the game itself made it super hard and a challenge just to get off the first level meaning the replay value was tremendous.
The idea was you guide (a caveman was it!?) your hero in a platform and collect the keys to get to the next level. You had a trusty yo-yo you could aim at stationery monsters whilst dodging balloons. Sounds simple enough but the jumping mechanism and sprite detection made this horrifically hard.
By far the best part for this rude 12 year old was when you died the caveman had a speech bubble which said 'FRAK!' which the parents were not all that pleased by when I went through a stage of repeating it whenever I made a mistake!
Looking back this was probably the reason I liked it, along with the huge graphical sprites as the game itself on replay is quite limited.