One of the main things which struck me as interesting was the definition of the character's attributes (called Values) via Traits and Orders... a grid which determines the character's nine Values, such as Strength, Agility, Endurance, etc. Looking at the grid, you can quickly determine how you'd like your character to be forged by assigning the priorities (1, 2, and 3) to each Trait and each Order. Then, it's a matter of drawing the lines from each Trait and Order, filling in the grid.
Skills are extraordinarily simple but well explained, within the context of the game's action resolution, which is, at it's heart, a roll under attribute X system, where attribute X is whichever Value the Game Master decides is appropriate. Skills provide a bonus to your Values for the purposes of action resolution, so a character with an Endurance of 5 were to be doing a marathon, having some skill in Jogging would definately help raise the chances of success when rolling the dice. Which brings us to...
The Bad
The game's system is not explained terribly well, and the game's writing can be downright painful, at times. I'm thankful the product is only four pages long... the writer needs an editor more proficient with proper use of the English language. This is not to say that the game's writing is slovenly, but things could easily stand to be made clearer, and examples in many areas would be a nice addition to the game.
The most glaring example of the game's poor writing comes in the form of the Opposed Rolls section, which was downright painful to read.
Another large problem with the game's design lies in the fact that both Shifters and Actions, which appear to be integral parts to the game's design, go entirely unexplained... as does the breakdown of time in the game. It's a gaping hole which the game sorely needs to fill.
The Ugly
First, a quick rant. The PDF Halo (d6) is distributed in is very, very basic. In fact, I'm sure I could reproduce it in it's entirety from nothing more than a basic text file, in five minutes using even a basic text editor. The system's logo is far from impressive, looking like something produced using MS Paint and some clipart. I'm not one to be picky about a game's layout, but the author clearly didn't even try. There are several graphics programs available for free online which could easily be put to use to spruce up the layout, but the author apparantly doesn't care to. A shame considering Eternal Tempest's site design, which is very nice.
Now, I've seen clunkier game mechanics than the one used in Halo (d6), but with the way this one was explained, I had to scratch my head and mutter "Wha?" for a moment... The game's author seperates Action Rolls from the Halo Mechanic, but the problem with this seperation is that the two are really part of the same mechanic, and to seperate them as the author does makes the writing hard to follow and causes the reader some confusion.
Then, as the mechanic's ideas fell into place in my mind, I took a long, hard look at "average" rolls and decided that the difficulty for rolls was faaar too high.
At the core, it seems to be your standard Roll 'n' Add dice system, and it is. However, the twist comes in the form of doubles rolled. The highest set of doubles is counted as a roll of Snake Eyes instead, so a pair of sixes only nets you a +2. When you're trying to roll under the values of your Attributes, this can be a great help.
The problem with the system, however, lies in the fact that there is no clear guidelines to how the distribution of skills should be handled at the beginning of play (so, Game Masters must invariably "wing it"), nor do characters advance often (it is suggested that characters advance 1 point in their Values for every 8-10 sessions). Skills aren't covered at all, and no method of advancement is suggested.
Now, assuming a character is performing an "Average" difficulty task (three d6's, keeping in mind the doubles), has a decent score in the relevant Skill (providing a +3 bonus), and has the average of his Values in the score, which would be 4. So, I have to roll under a 7 on 3d6.
I tried it out, grabbing 3d6 and rolling the dice thirty times to see how often my character would succeed at a task deemed "not-to-simple" (another example of the game's spotty writing).
For a task that was reasonably easy, and for a character with a skill nearing half of the +7 maximum, I failed 21 of thirty times... 14 of the failures were so disgusting (10 or more) that a character with the maximum starting Value (6) in place of the average Value (4) would still fail. So, at a "not-to-simple" task, the average person will fail roughly two thirds of the time. The odds get even more and more stacked against you as you get to the Difficult (4d6) and Near Impossible (5d6) levels... Near Impossible being so stacked against you, that a prime example of the human species (Value 10), with a maximized skill (+7), would still have a fairly reasonable chance of failure.
It's a shame that the difficulty is so skewed against the player and the skills section is devoid of any form of development... the system looked to be fairly promising.

