Jetpac was originally released for the ZX Spectrum back in 1983 which was developed by "Ultimate: Play The Game" which eventually became Rare. With Jetpac Refuelled, the original game is packaged alongside a new rebooted version for modern audiences.
In the original game, your goal is to build a rocket by collecting the two pieces, then collect fuel and bring them to your ship to launch your character to the next level. Enemies spawn frequently from the sides of the small playing area (screens were small back in the old days), and you can shoot them to defeat them. The small playing area is what makes the game incredibly tough since you have to be extremely cautious when collecting fuel from the edges of the screen, because this is where enemies spawn; resulting in many cheap deaths. You build a new rocket only after completing four levels with your existing rocket, so the three levels after each rocket-assembly level only have you collecting fuel.
In Refuelled, the screen is made much bigger; meaning the camera has to zoom out slightly as you reach the edge of the screen. Enemies can spawn everywhere and they spawn at a much higher frequency. There are power-ups which change your laser fire, in addition to screen-clearing bombs. The levels where you are required to assemble a new rocket act as check-points, allowing you to continue the game when you die.
There are a total of 128 levels in Refuelled, and the game is incredibly tough so you will only clear a few levels before dying. The difficulty is completely erratic though, with some levels being virtually impossible before going on a run of easy levels.
There's plenty of different enemy types which have different movement patterns, so some levels require a specific strategy. You may need to be more aggressive at taking out enemies otherwise you will be overrun. Other levels start off with the screen completely covered in enemies. The only way you can beat the level is to use your bombs. But what if you don't have any bombs? You are gonna have to accept that you are going to die and will need to do the last few levels again but save your bombs. This is completely unfair game design.
I thought the laser power-ups seemed quite bizarre. You go from a normal laser, to one that has an additional beam that fires vertical, the next has three lasers, but the next goes back to one laser albeit more powerful. This means you go from being able to clear out multiple enemies at different heights quickly, to only be able to take out a few enemies that are in front of you. This is a huge disadvantage in the majority of the levels. It's also annoying that dying or completing the level resets your gun. This can mean it's impossible to complete a level if the screen is flooded with enemies.
They have also gone a bit overboard with the graphical improvements. There's so much going on with the lighting effects that it often obfuscates enemies. The Fuel have a pulsing light surrounding them which often hides enemies, leading in cheap deaths. There's even certain enemies that are semi-transparent, which intentionally blend in with the background. When lives are so precious, throwing 'dick-moves' at you like that is completely out of order.
Although I liked the concept of the game and I have fond memories of the original, I found Jetpac Refuelled to be fundamentally flawed. The spawn rates were usually set too high, and the difficulty didn't seem well thought out. The levels should get progressively harder rather than been completely arbitrary.
Despite the attempt to bring the game to a modern audience, I think this is a game more suited to fans of the original game.