Similarities to Gradius
Life Force shares a lot of similarities when it comes to the way you progress through each stage. You must survive the stage and defeat the boss at the end before proceeding to the next stage. Even the manner in which the stages occur are similar. They possess the same three components as the stages in Gradius do:
- The pre-stage is typically a short period where squadrons of enemies will appear. During this time, power-ups will be awarded to the player for every squadron that is completely destroyed. This is meant to help power you up to a reasonable level of offense before the stage truly begins.
- Each stage has it's own unique properties, but in general, your goal is to survive the trip through the stage, which scrolls automatically, while you attack a variety of enemies, and dodge their return-attacks.
- At the end of each stage, you will be forced to fight the boss of the stage and defeat it in order to reach the next stage. Bosses usually possess a single weak point, which must be shot at continuously in order to destroy the boss. They also typically present a very strong defense and attack you quite aggressively.
Differences from Gradius
In Gradius, when you die, the action stops, and you resume play from the beginning of the stage, or from some predetermined check point. You also lose the benefit of your power ups. In Life Force, when you die, the stage continues to scroll along, and your next life speeds onto the screen to replace your fallen ship. You will get a brief limited period of invulnerability at that time. Additionally, any options that you were in control of will suddenly turn green and become available for either player to collect. That means in a single player game, you can resume control over your options if you manage to collect them before they scroll off the screen. In a two player game, the options become fair game for any player to collect.
Stages only scrolled horizontally in Gradius. Salamander also introduces the concept of vertically scrolling stages. However, this difference is merely visual, and does not drastically change the overall strategy that one should employ in order to survive each stage and destroy enemy ships.
Differences from the arcade version
Unlike the arcade version, the NES version does not use the instant power-up collection method seen in Salamander. Instead, it uses the traditional power up method found in Gradius.