I am working on an action game in which the player receives a fixed score for performing the main game action successfully. However, the player can also receive a bonus based upon the length of time he continuously performs the main action, and another bonus based upon the length of time he performs a secondary action while performing the main action. While creating the formula for computing the total score, we had some disagreement over whether each bonus should be used as a multiplier to compute the main score or whether they should be added to the main score. One school of thought was that using multiplier might make the scoring difficult to balance, where the influence of the secondary action might be lost on the player, or on the other extreme, might make the score range too wildly. Another school of thought was we should use a multiplier for the secondary action, to better reward the player for simultaneously performing two actions. So, under which circumstances would you use a bonus score as a multiplier, and when would you use a bonus score as an addition?

I agree that using it as a multiplier will make it too radically different. That would create only one strategy to get as high of a score as possible, unless you are talking about 1.05 - 1.1 multipliers (which I doubt you are). By only adding it, this is giving the players more space to determine their own strategies for getting a high score.

What happens when we add a bonus vs multiply a bonus?

Adding produces an overhead, offset type effect. Early on, the added score might be a big chunk of the total, but later the added amount is a smaller part of the total. Like lighting a fire with a match, eventually the match is tiny by comparison.

Multiplying produces a percentage type effect. Early on, the percentage might be smaller number of absolute points, and later the multiplied amount has the same basic pizza slice relationship to the whole, but more cow bell.

What I am thinking is if the game gives a bonus multiplier for doing the secondary action, say x2, x3, x4, etc., then the secondary action *has* to be done in order to get a high score, and it must be done efficiently along with the primary action. If the secondary action simply adds a bonus, then this allows the player to experiment more. What if they completely forget about the secondary action, and try to complete the primary action constantly, at a high rate of speed? What if they do primary twice, then do one secondary as fast as they can, and go back to primary? This would give a lot of freedom to players to find a strategy.

A real-world example I can think of is Tony Hawk's Pro Skater vs. EA's Skate. In THPS, doing a trick combo into a manual into another trick combo gave you huge point modifiers (x2, x3, x4, x5 and so on). To get large, competitive scores, you *had* to use manuals, and you had to use them every time. If someone was not as good at manually, they have automatically lost against another player who is good at them. By contrast, in Skate, huge modifiers are not predictably given out by a formula for using one tricky gameplay mechanic, so the field is much more even. An advanced player will still typically win over a newcomer, but there is not a huge disparity in the scores.

Some excellent feedback. Thank you!

I, personally, have been leaning toward an additive bonus, because I think it allows for more strategy.

Using the skateboarding example given above, say you have a variety of tricks that you can do. But if you also did a spin while doing the trick, you get a bonus. As someone pointed out above, using a spin as a multiplier bonus, players would be forced to do a spin each time to get the highest score.

Also, consider each trick having a basic spin score that increases for the number of degrees you spun. Some tricks might really benefit from spinning; others not so much.

The more paths there are to a high score (or conversely, the lack of a single path to a high score), the better balanced the game is.

IMO, this really depends on the kind of game you are developing. Additive and multiplicative score bonuses both have different purposes and should be used when appropriate - there isn't a better system of the two.

The purpose behind score bonuses is to provide further reward for extra achievement. In a game which relies on style and technique - like skating games - a temporary score multiplier is appropriate because it is used to award persistent good play and expertise. This means they have maintained their streak of prodigious play for an extended time without mishaps. When they make a mistake, the streak ends and they have to build it up again (encouraging them to play with a good mastery of the game). It also further increases the embarrassment at having made a mistake in a game which mimics a real-life sport where image counts. The score amounts do not become unwieldy because they only apply to score awarded during the streak, and do not multiply the player's total score. This system is also appropriate in bullet hell shmups and rhythm games for the same reason.

Note also that this system of scoring is rooted in arcade gaming paradigms. These games are typically competitive when it comes to actual score numbers (they may record and show a public high score table). Due to the nature of multiplied scores, there is no absolute maximum score for a playthrough - or to achieve it would be difficult or nigh impossible. Players thus compete to get the highest score on the list based upon their skill at playing the game, and look good doing it too.

Additive bonuses are appropriate when you have determined that there is an absolute maximum score, or can be given arbitrarily for collecting or achieving something during play. They are typically one-off bonuses rewarding the player for completing an action. Shmups often give additive score bonuses for picking up floating medals, or destroying optional enemies and bosses. They can also be added when the score is tallied after a stage is completed for good performance. Platform games often do this for completing a stage in a short time period or for completing particular optional areas.

In short: multiplicative bonuses for continued skill, additive bonuses as a direct reward for achievement.

Primogen, you haven't told us what causes multiplier to fall.

The usual setup would be that any failure resets it; whether to use high multipliers in a game then becomes, "is the game still fun to play (to a skilled player) when they have to avoid the slightest failure?".

It's true that a high multiplier which the player has to maintain (such as by chaining) lest it reset tends to force a narrow range of tactics on the score-minded player, but multipliers don't need to be built that way. You can have a low cap on the multiplier; you can have it decay at a constant rate; you can have it reset in reaction to something else than damage/style failure/etc. Lots of options.

I personally see flat-only bonuses as boring. They are too simple to add much strategy to the game. At its best, a well-crafted score system can make such a huge contribution that playing for score feels like a different game (in the positive sense) compared to playing for survival.

One more thing to consider: do you want your score mechanics to support survival (doing what's best for survival gives highest score), tempt the player to take extra risk to obtain higher score, or something in between?