Let me begin with a few pointers that I wish I had known going into Helen's Mysterious Castle. First, fullscreen mode (accessed by holding Alt and pressing Enter) caused horrible stuttering on my system and I know I am not the only one. The best way around this that I found is by using Windows Magnifier. You can trigger this by holding the Windows key (between left Ctrl and Alt) and using the + and - keys to zoom in and out. By default it zooms in where your mouse cursor is located. On a 1440p monitor I found +325% zoom to be just right.
Second, the main character, Helen, is illiterate at the outset of the game. You can learn to read, but it is easy to miss and cannot be unlocked by backtracking late in the game. I've written the following instructions vaguely enough that I wouldn't consider them a spoiler: When you first unlock the second shortcut back to your home there will be a new gravestone nearby. Examine it for a cutscene where, among other things, Helen is taught to read.If you don't do this you'll miss out on some nice tidbits of lore that help to more fully illuminate what's really going on in this mysterious castle.
The third and final tip: After fighting the Undead Knight, there seems to be a common game crash that is avoidable. It happens immediately after the battle when entering a double doored cathedral through the left door. The right door does not seem to be affected by this crash, but it's worth saving your game just in case.
Now, on to the actual review.
This little gem of a game's brightest aspect is its battle system. Combat encounters are elegant duels that have you constantly switching tactics in order to counter your opponents moves. I will leave the details for you to discover on your own, but in short you have 8 inventory slots to fill from a collection of equipment that includes bows, swords, shields, various magics and passive stat boosting items. You will need to keep a diverse selection in order to be successful.
You find new items at a steady pace throughout the game. Many of them are in optional side areas. As you gain experience in the game, you do not level up yourself, but instead use your experience to upgrade your equipment. This grants a satisfying sense of progression that gives you frequent, small boosts in power.
The combat isn't entirely flawless though. First, fights are only ever 1 vs 1 affairs. The mechanics don't lend themselves well to having numerous participants. Second, once you've found a winning strategy against a particular monster, you can usually easily repeat the process on successive battles with that opponent type. This is both good and bad in that it rewards you for skillful play, while also making further battles less engaging. These are minor complaints that are largely counteracted by excellent boss encounters, many varying enemy types and the relatively short length of the game.
Uncovering details about this game's castle setting and its inhabitants is a joyful experience. You are set loose in the beginning with no exposition and only slowly learn the true nature of this place and its people. There are a few minor writing errors, but the script is otherwise skillfully woven in a way that, as more information is revealed, you can look back on some previous conversations and see deeper meaning in them. The story is often cute, relatively lighthearted and even comical at times but it is not without touching moments and serious topics. Visuals and sound commendably convey the emotions of the scenes, albeit in a familiar SNES RPG style.
In addition to being illiterate, Helen also speaks with only two symbols, "?" and "!". This gives the sense that she is also mute, making her hard to relate to as a character but easier to apply your own personality to. I didn't care for this design decision. Regardless of this, she does have a short but interesting past that's tied into the plot. Most other characters are enjoyable but the game isn't long enough to give them great depth. There is one character that I won't reveal the identity of that is the main focus of the story. We get to learn a lot about them, even more so if you unlock the ability to read.
I ended up playing through this game twice. My first playthrough took just over 6 hours to complete while the second was a little over 3 hours. I actually accomplished more the second time through despite taking half the time. Unfortunately this game is occasionally unclear with its directions on how to proceed. Two instances in particular had me lost for a significant amount of time before discovering that the way forward was through a hidden passageway. I only discovered these by mindlessly running into walls in the general area that I thought I was supposed to be in. I wouldn't call that good game design and it artificially pads the game length.
There is decent replay value to be found here. Trying out different equipment builds can be fun. There is enough hidden and optional content that you'll likely find new things the second time around. In the credits there is a hint on where to find the entrance to a dungeon with the hardest enemies you'll encounter in the game. There are even two endings (that I discovered, at least). One is definitely more satisfying than the other but it is easy enough to move from one to the other without replaying the whole game.
With such a low price tag this is an easy game to recommend!