Sentinel is an oddity among 7800 games in that it is the only game not to be released in the US. Due to the collapsing market for the 7800 in America, Sentinel was only released overseas in PAL format. The 7800 version of Sentinel is very similar to the 2600 version (which was released in NTSC format), but with the expected graphical enhancements. So did American gamers miss out on one the best 7800 games ever to grace the console? Not really...
Sentinel is a shooting game that plays like a side scrolling version of Crossbow (which was also released for the 7800). However while in Crossbow you had several people to protect as they walked across the screen, Sentinel only has one large orb for you to protect. As your orb (known as the Sentinel) moves steadily across each enemy planet, it will be under attack by numerous small aliens. You goal is to protect the Sentinel from getting hit at all costs. However given the speed of the aliens and inaccuracy of the light gun, this isn't an easy task.
The Sentinel was built to absorb all the energy from the alien planet (sort of like that Crystalline Entity from Star Trek). This is accomplished by shooting the enemies on the screen. Enemies in Sentinel come in two flavors, air enemies and ground enemies. Air enemies will either attempt to ram the Sentinel or will hang back a short distance and shoot bullets, while ground enemies will always stop and shoot at the Sentinel. Accurately shooting all the enemies on the screen as quickly as possible is the key winning this game, as the longer you let the enemies congregate the quicker you will be overwhelmed. If things begin to get out of hand you can shoot the Sentinel itself to set off a super bomb which will destroy all the enemies on the screen. The super bomb can only be used when the word READY lights up next to the super shot meter.
As you progress deeper into each level you will begin running across power ups. Power ups appear as odd looking square boxes that fly at the Sentinel. Shooting these boxes will give you one of these bonuses:
If you've purchased a copy of Sentinel, then you've undoubtedly noticed that the manual included with game looks odd. This is becuase Sentinel was released so late in the 7800's lifecycle that Atari didn't even bother printing a professional manual for the game. Instead they simply copied the prototype manual (complete with placeholder text), and packaged it with the game. This is most likely because Atari was desperate to get the carts they had manufactured out the door by any means necessary.
While Sentinel isn't a bad game by any stretch, it just lacks the variety needed to make it a great game. The background and enemies may look different from planet to planet, but they all have an oddly familiar feel to them. The giant bosses at the end of each level are a nice touch, but even they start to produce a sense of deja vu. Repetative level design combined with Atari's highly inaccurate light gun make Sentinel an average 7800 at best.