Multiple Features: The Reel Make-Up

Feature Reel Strips

Feature reel strips should not, in well-designed games with good reputable software, be made worse than the reel strips used in the base game.

Players chase features, and to reduce feature payouts in order to make the feature hit more often just makes for a game with limited volatility and appeal.

Getting features that pay very little does occur (can’t avoid it in a random game), but it’s good to at least minimise the chance that it’s going to occur. I personally strongly favour improving reel strips, where possible. Even though this adds to the average RTP component being “used” by the features it increases the impact the features will have.

Adding substitute or scatter symbols is typically the path followed. In some cases the game mechanics just don’t allow this, such as when a feature is already so powerful that it would require far too much of the RTP to overtly improve.

Reel strips shouldn’t be changed aggressively unless it’s advertised to the players in the game rules, such as “all of such and such a symbol are changed to (x) during free games”. I’ve noted a popular game at the moment that uses a frequently hitting free game feature with cascading reels changes their reel strips completely when the feature is activated. Pretty obvious when the symbols are changed from their triggering combination the instant the first free game starts to spin, and the symbol combinations that are subsequently likely are far and away worse than in regular game play.

Occasionally you’ll have to change a feature strip slightly to achieve viable game play, but making reels strips dramatically worse in feature play is a no go in my opinion.

Feature Triggers and Line Activated Features

The most common trigger event on a 5 reel video slot is achieving 3 of a particular symbol in any location on the reels. It’s a fairly easy trigger mechanism to juggle to an appropriate hit rate and heightens player anticipation, as all 5 reels come into play rather than just the first 2 or 3.

That’s not to say that other trigger events can’t also be effective.

A line-based trigger, such as “3 (n) appearing on a played line from left to right triggers the feature”, allows for a feature prize that will be calculated on average expected return on a single line basis.

Let’s say that the line-based event is a straight “pick and win”, that yields a prize of up to, say, 1000 times the line bet. In this instance a probability schedule is again going to be used, and a prize from that schedule will be awarded on the pick. The base prize would be multiplied by the bet per line and awarded, so if a player is betting say $1 total, with 20 lines in play, the prize awarded from the schedule would be multiplied by 5c.
The expected RTP from this feature is calculated in the same manner as other features:

Probability of trigger * average expected prize = RTP

However, the average prize if a pick feature is going to be higher and the probability of trigger proportionately lower than in a scatter trigger. A trigger rate of say, 1 in 2000, is going to yield an average trigger rate of 1 in 100 spins if playing 20 lines, assuming no coinciding lines result in trigger combinations.

An average prize of say 400 (times line bet) will then result in RTP consumption of 20%.

If the trigger combination leads to free games I’ve found the best mechanism is to always have maximum lines in play during the feature event (such as in RTG Fruit Frenzy) In a straight-forward free games feature on 25 lines with say an average of 15 free games including retriggers, with an average RTP per free game of say 150%, the RTP from the feature will be 25*15*150% = 56250%

If a trigger rate of say, 1 in 2500 was used (based on single line play), the overall RTP consumed would be 1/2500*56250%, yielding 22.5%.

In this instance the trigger chance versus return is entirely proportional to the player’s wager given the number of lines the player has opted for.

A player on 1 line will have a 1 in 2500 trigger chance, but will then get 25 lines in play and an average return of, in this example, over 562 times their bet. A player on 25 lines will have a 1 in 100 trigger chance, and will receive 22.5 times their bet on average as the total prize. The return versus bet is balanced by the proportional shift in average trigger chance.

In all instances one pick should be awarded for any coinciding line triggers. So if the trigger event occurs on 3 different lines in play at the same time, one feature event should be awarded for each of them.

An alternative does exist to simply multiply the result by the number of coinciding triggering lines…but when you’ve gone to the trouble of getting the feature I think it’s far more satisfying to play out the multiple rounds.