Strategy and upgrades are at the forefront in Sentinel 4: Dark Star, a tower defense game that challenges players to think on their feet in campaigns. There are 26 maps in the game, each with their own interesting challenges. Some of these challenges include limited locations to set turrets up at and other unique strategy requirements. Sentinel 4 is compatible with iOS devices running 5.1.1 or later.
There are two modes in Sentinel 4: campaign and endless. Each mode can have one of four difficulty levels (easy, medium, hard, and psycho). Easy mode is a nice introduction to the gameplay and enjoyable for people new to tower defense type games or those just wanting to play a less challenging level. Medium mode is a good intermediate mode and a stepping stone in difficulty between easy and hard. Enemies become stronger in hard mode and this increase in strength seems natural, adding a new challenge. This is especially noticeable if you are replaying a level you recently beat in one of the easier modes. In psycho mode, each enemy is much stronger and they take a lot more hits to be taken down. It is much harder to get a good defense started and also harder to continue building up that defense.
Sentinel 4 rewards players with more weapons, upgrades, and enemy types when they continue to beat levels and progress in the storyline. There are four categories for the weapons (turrets, path, sentinel, and stronghold). The turrets are the basic line of defense for your base and they become stronger the further along in the game you get.
The next category of weapons is path, these are droids that can be used in the middle of pathways to block enemies from progressing very far without being damaged. Sentinel weapons are used by the sentinel to attack enemies with more powerful blasts and repair structures and turrets. Finally, the stronghold weapons are similar to the sentinel weapons but is usually stronger and takes longer to charge.
All of these weapon categories can be upgraded with anything from auto-repair to increased range and duration of attacks. The upgrading in Sentinel 4 is a lot of fun and enhances the gameplay considerable as it makes the strategy more important.
Sentinel 4 features stunning visuals and effects as well which accents the gameplay nicely. The way the lava moves is visually interesting and the lighting looks very natural with the setting of the game. Level progression flows very nicely and fits well with the storyline. However, even though the story fit with the gameplay, defending the base seemed more exciting.
Each commander you pick has its own special abilities. For example, the Hyperion, which can be unlocked after completing some campaigns, has the ability to convert enemies killed within its range to energy to charge up your Sentinel. You can upgrade each commander's strength, guns, and tech capacities each with their own benefits depending on how you will be using the commander.
Depending on what the level's layout and enemy patterns are, you have to be prepared to adapt your strategy and be conservative with your efforts as a lot of the time you will be limited in your resources and have to make tough decisions. When a level has more than one gate protecting the Sentinel, sometimes you have to make the conscious effort to let the first gate fall in order to protect another area that is getting overrun if you only have enough money to build one turret.
Building strong but agile strategies is crucial in this game and with so many options for upgrades Sentinel 4 feels more challenging and addictive than some other tower defense games. Sentinel 4: Dark Star is available on the App Store for US$4.99 and I would highly recommend picking up this addictive game.