we've talked a few times before about
the use of randomness and skill based
games but James had a couple of designer
friends asked us to go really in depth
on it to really on a fairly technical
level dive into how a random chance
affects the players experience of the
game and how you build a random element
into an otherwise skill based game so
randomness does three things first it
creates exciting moments second it
occasionally lets the weaker player win
third it forces players to adapt to
circumstances rather than always follow
a plan as you build randomness into your
game you have to decide which of those
effects you're going for so you can
emphasize it with the specifics of your
design once again I'm going to use
hearthstone as an example of this
because hearthstone is a game where all
of the randomness is right there on the
surface and very visible to every player
but no matter what game you're looking
at the same principles apply basically
all of these things come down to the
Delta of randomness now you may think
that the Delta of randomness simply
refers to the difference between the
maximum and minimum impact a given card
can have on play but it's actually a
little more complicated than that it
actually refers to a given cards maximum
and minimum distance from the power
curve now sometimes this is easy to
judge for example a card like fist of
jaraxxus is so far below the curve that
even if random chance gave you the best
possible result it would still not be
worth playing most of the time though
cards with a random effect will fall
both above and below the curve and
that's where accurately determining a
cards Delta of randomness becomes a lot
more complicated see having an
unpredictable effect is inherently
negative for the player it prevents them
from planning around exactly what's
going to happen and thus it can't be
counted on in clutch situations this
means that for a card with a random
factor to be even remotely playable the
random effect has to have some upside
that'll put the card above the curve if
it goes off but the fact that these
cards have to have an above curve upside
means that the designer has to balance
for that possibility which in turn means
that cards with a positive random effect
have to be tuned to be below the curve
if you ignore the random effect because
after all if a card that already sits
right on the power curve is given a
random chance of simply being better
sometimes that random chance bumps it up
above the
power curve and threatens to push out
other cards so that leaves the question
of the Delta of randomness how far above
the curve and how far below the curve do
you balance a card that involves some
random chance
the further above the curve you allow a
card to go and the more likely the card
is to have it's above the curve effect
the further below the curve you have to
make that card in its default form when
you ignore the random element and as
that Delta gets wider and wider as a
cards potential to spike above the curve
increases the more you have to
incorporate chances that the random
effect won't make up the difference
between the base card and the standard
power curve because otherwise again the
card would just be above curve the
larger you make that Delta the swing
year the card is that is to say the more
likely it is that a player will lose the
game if the random element goes badly
for them and the more likely a player is
to win the game if the card randomly
does well now you could argue that this
creates exciting moments like playing an
unstable portal and pulling out exactly
the right legendary card that sort of
thing does feel exciting but the problem
is that often these moments are exciting
for only one player a bad result on the
randomness table in this situation is
fun for nobody and a good result may
give one of the players a bit of a rush
but it's just going to leave the other
player feeling like the game was unfair
and that's not the result you want as a
designer exciting results can actually
be much more consistently produced from
smaller Delta's and randomness because
when the cards aren't quite so swingy
players don't immediately dismiss a
matches result because of one good or
bad roll of the dice for example let's
say spell slinger gets played which adds
a random spell card to each player's
hand if one player draws a board
clearing flamestrike and the other
player draws deadly poison when their
deck doesn't even have weapons to use it
with that's not really exciting it
doesn't create a grand moment it just
made the game feel arbitrary on the
other hand take something like flame
juggler the Delta of randomness there is
pretty low if you ignore its random
effect it's just a - strength 3 health
minion 4 - mana cost which is just
slightly below the curve factoring its
random effect in at its worst this is a
2 3 4 - that does one damage directly to
the opponent hero's face which isn't
great but in arena mode that's still
totally playable and even in a best-case
scenario where you're playing a 2 3 4 -
that does 1 damage to a target enemy
minion when played that's quite good but
it's not game breaking now as a player
about 20% of the time your
just going to be playing this card as a
2/3 minion because you just want a 2/3
minion on the board you don't really
care about the random effect and that's
fine about 60% of the time you play it
you may have a specific target you'd
love to see take that one bonus damage
but even if you get your way it's only
going to change play a little bit but
that last 20% of the time when you play
this card that one damage could mean all
the difference in the world and you've
got your fingers crossed and your
opponent just doesn't breathe until they
see where that random damage goes and it
just creates this intense moment that is
awesome and it's exactly how a
randomness should work the reason that
this is such a great example of ideally
designed randomness is that even in that
20% case while one point of damage
hitting the right target can indubitably
have a big impact on the game it's never
going to win the game by itself the
player is going to have to capitalize on
the advantage that lucky role got them
by following it up with board dominance
in the early game or finding a way to
have it help them stabilize things in
the late game but it's never going to
simply end the game on its own it may
put a player who's already behind even
further out of reach of catching up or
it might give a player who's on the
verge of defeat a small chance to
stabilize but the randomness on the card
doesn't become the game in and of itself
and so those moments are still exciting
for both players giving them both
something to hope for or to fear so in
general you want a low delta of
randomness not necessarily zero and it's
not that the higher the delta of
randomness is the worse it is what I'm
saying is that for every game there is
some line passed which - hyah Delta
creates a feeling of being arbitrary
rather than exciting one important thing
to note here is that a good way to deal
with this is to give the player a way to
shrink the Delta of randomness through
play bomb laba is a good example of this
it's stats are certainly far below the
curve for a 5 mana card but the fact
that the player has the opportunity to
eliminate the randomness from this card
entirely by trying to reduce the
opponent's board to one minion before
playing it makes it a card that's good
in arena and yet can still give those
exciting hope and the prayer moments
where the player throws it out without
being able to temper the random chance
and just crosses their fingers the
design here is particularly strong in
that the only time the player will ever
really use the random element of this
card is when they're behind allowing a
good random role to help them catch up
but not giving an extra bonus for a good
random role to players that are ahead
I've actually got a lot more we'd like
to cover here symmetrical randomness
which is kind of an oxymoron but
whatever negative randomness and there's
a lot of cards that are concrete
examples that I'd like to dive into as
well but we're kind of at a time so join
us next time for all of that and a more
thorough discussion of spell slinger and
after that we'll lay off the randomness
discussion for a while
promise see you next week
Oh