This is the Master System conversion of the MSX game Aleste. Why the name has been changed to Power Strike outside of Japan is beyond my knowledge. The story is the same, but without the girlfriend component. Some genetic experiment got out of bounds and mutated plants endanger the lives of millions, blah, blah, blah.
The game is almost identical to the MSX version, except that the colours are a bit brighter, the score-meter looks better and the main weapon is harder to power up. However, for unknown reasons, the initial city level is missing. This leaves a total of six stages (not counting the hidden bonus stage zero, which is the same as the first, only that the colours are weird and it scrolls about twice as fast). The game actually starts with area two of the MSX counterpart. Unfortunately, the nice anime-style intro of the MSX version is also missing. And some of the secondary weapons have been exchanged. So the very cool weapon number five has been replaced by an utterly useless homing missile, but the web gun (number six) is much more powerful. Other weapons just look different (which means that they look a lot better on the Master System). The bullets of the secondary weapon systems are bigger on the Master System, but they do less damage and they time out much earlier. So the Master System version is a little bit tougher than the MSX original.
Like in all games of the Aleste series, in Power Strike your space ship is armed with two weapons that you fire seperately by pushing the appropriate buttons on your control pad. The main weapon is a tiny little energy blast. It can be powered up by collecting 'P'-symbols that fall out of certain enemy ships. Isn't it funny how the enemy always provides your supplies? Seems to me like this is a major flaw in all the world conquering plans of various alien empires throughout shmups history. The main weapon can be powered up to a double and even a triple shot.
The secondary weapon comes in eight different flavours (a variety of lasers and plasma balls). You can chose the secondary weapon you desire by simply collecting one of the numbers 1 to 8 that can be found along the way. Collecting more than one of the same number increases the power of your secondary weapon. Unfortunately, the secondary weapon can only be used for a certain time. If you don't collect another symbol of the same number before its time runs out, your secondary weapon simply switches back to the default weapon (number one) in its lowest form. So, although I like the laser (number 3) and the web gun (number 6) better, I usually stick to the default weapon, simply because it never runs out of time. It's also reasonably powerful. If powered up thrice, it can destroy enemy bullets, which is crucial if you want to succeed.
What I like most about the game is that it has some built-in AI. The more you're powered up and the higher the frequency of your shots, the more enemies are sent to stop you. The game adjusts the difficulty level 'on the fly', so no two games of Power Srike are ever exactly the same. This gives the game almost unlimited replayability. However, it doesn't make it any easier. Given the fact that Power Strike is one of the tougher games around, it can be a little bit frustrating if you are actually being punished for playing good. The game is very fast. There are tons of sprites on the screen and there's hardly any slowdown or flicker. Apart from the technical aspects, I like the straightforwardness of the game. There's no messing around with speed ups and stuff, no background elements you could crash into. Just pure adrenalyn-laden action and fun.
Not only are the graphics really nice, the sound is fine, too. There's some really good tunes that perfectly match the manic pace of the game. The best track is the music in the ending sequence. The sfx are likewise wonderful. Roaring gunfire, powerful explosions. All is done very well.
However, there are some things I just hate about the game. I hate it how the extra symbols float towards the top of the screen, so you have to dart forward to catch them before they disappear, often crashing into enemies you just couldn't see. I also hate it that the extra weapons don't last indefinitely. If a secondary weapon runs out of time, it usually leaves you amidst a plethora of foes armed with nothing more than your crappy default weapon. This results in certain death. Additionally, if you lose one life, you lose all your power-ups. This means that you lose all extra lives shortly after, because you never get powered up quickly enough to have only half a chance of standing up against the enemy lines. So you either play the perfect game and beat Power Strike without losing a single life (which is, in fact, possible), or you don't make it at all. The same is true for the continue option. You've got unlimited credits, but they are of no use at all, because beyond level one you just don't last long enough to get powered-up properly. Another minor flaw of the game is that there are no real bosses around. All you get for a boss is some group of ground bases. Bah.
But apart from these minor flaws, Power Strike is a really entertaining shooter. Although the cart is pretty hard to obtain these days, it's definitely worth looking for.