So, for a film class, I got permission to produce a 2D video game. I am instructed to focus on the screenplay BEFORE focusing on gameplay elements. As such, I am building the game in response to a custom script.

Story: Detective kills a man for the first time while on duty, is subsequently cursed through accidental circumstances, and as a result of the curse, spontaneously murders those around him when his emotional state wavers significantly. While pursuing the mystery of how to remove said curse, the detective dodges the suspicion of his co-workers around the ongoing serial murders and struggles over his inner feelings of guilt and weakness.

Now, I'm expecting the game to be an interactive drama, so I am going with the convention that the player will walk around a 2D environment, talk with NPCs, interact with items in the environment, gather clues in an inventory-journal combination, and have a relatively linear story to minimize production costs and effort.

My hope is to devise gameplay elements that are targeted at generating in the player the emotions that the protagonist is feeling. Namely, the protagonist feels that he is losing control of himself and as a result is losing to a darkness inside attempting to overpower him.

Here is a list of tentative gameplay mechanics I have considered incorporating. I was simply hoping for your guys' thoughts about their effectiveness...

1) a heartbeat sound is played whenever the character fails a task (not necessarily the player as sometimes the story line events will make the character feel guilt / weakness as well) and the camera momentarily zooms in on the player, alerting the player of the curse gaining more power for a potential rage.

2) If the curse becomes too powerful, the protagonist will begin some type of aggressive action automatically (power quantity will be indicated by a heartbeat counter in the corner of the screen as well as frequency of sound effect during "mishaps" in player action or simply the automatic story events). The player will be able to slow down, pause, and eventually/possibly prevent the continuation of whatever the animation of the character is (pulling and aiming gun, assaulting someone, etc.) by pressing certain buttons on the controller. Attempting to model this activity from things such as Beyond: Two Souls or the end snowy mountain sequence from Journey, etc.
3) After any "rage" incidents, the curse's power is abated for the time being (w/ curse power level reset to 0).
4) Most of the time, it would require the players skill to prevent "attacks" from happening, but if the curse power becomes too large, then the player would be unable to completely prevent a given atrocity.

Are there any unforeseen complications I may not be seeing? Does this sound like a mechanic that can get the player invested in the sense of success / failure that would be felt by the protagonist?

[Ignore this section] - previously contained an entirely separate post, and it was moved here for some odd reason. I'll just re-post it in a few days or something.

The player will be able to slow down, pause, and eventually/possibly prevent the continuation of whatever the animation of the character is (pulling and aiming gun, assaulting someone, etc.) by pressing certain buttons on the controller.

Are you referring here to quick-time events? If so, then perhaps approach with caution: there are players (myself very much included) who have a strong dislike for quick-time events. Additionally, I feel that, save perhaps for some very well-designed exception, quick-time events reduce a game's immersion by virtue of focussing the player on the interface rather than events in the game; since immersion seems likely to be somewhat important in your case (since you want the player to share the character's emotions), this feels especially important to me.

Hmm... If the aim of the mechanic is to allow the player to calm their character, then perhaps give the player actions that they can perform to calm the character: take a deep breath, sniff a bag of lavender and so on (of course, if the player is particularly involved in a scene at the time (especially if said scene involves a task that calls for concentration) then it might be easy to forget or tempting to put off the use of such devices...).

When an "attack" (so to speak) is imminent, they might be able to fend off their wandering hand by directly deflecting it: the camera focusses on their hand, and the player has to deflect their hand via movements on the controller (the exact choice of control inputs might depend on your interface--if you were using mouse-based point-and-click gameplay I might suggest moving the mouse, for example). This is similar to the quick-time solution, but I feel that it's more organic: the player is using the established interface, and responding to the events in the scene, rather than arbitrary button-prompts.

How do the people around him respond? Is the player going to mindlessly kill NPCs on the street?

Actually, in combination with my "deflection" idea above, this gives me another, related idea: instead of preventing an "attack", the attack happens, and the player's task is to prevent injury or death resulting by using the controller to deflect the character's aim. This may sound easy, but if there are multiple bystanders around it could be all too possible to accidentally deflect a shot from a specific target, only to have it hit someone else.

Thanks a lot for the input. I like Thaumaturge's statement here:

he camera focusses on their hand, and the player has to deflect their hand via movements on the controller

And Kseh's idea of the "fast paced puzzle thing" is a bit similar to what I'm going for. I wasn't initially thinking of quick time events per se (cause I generally don't think they are as effective either), but I was more thinking along the lines of what occurs in Heavy Rain in "stressful situations": the dialogue options that are mapped to the controller buttons and which USUALLY are overlayed over the screen in a static state instead begin shaking like crazy and swirling around the player's head. It effectively keeps the player in "control" of the story events, but the chaotic nature of the game feedback makes it more difficult for the player to A) read and therefore decide what to do and B) evaluate which button corresponds to the desired statement they read so that they can press the button. It mimics the confusion experienced by the character (probably one of the only mechanics from Heavy Rain that were especially done well). I should have been more descriptive. But does that sound like an acceptable mode of delivery for a player response opportunity?

@Kseh
The game needs to last less than 10 minutes, both for project goal and logistical/resource reasons, so there will only be a few instances where the player can potentially kill someone (at most 3). I plan on arranging it where the player will only ever have the ability to kill one person at a time, so that each time they are experiencing the struggle of simply taking a life, just as the character does initially. They are effectively re-living the experience in an exaggerated form. And I'll attempt to have minor changes to the story line, but I can't afford to have too much of a branch. It'll have to tie back quickly to a linear path (again for resource reasons). I'm the only one working on the project.

@Thaumaturge
That's an interesting idea...but when I think about it, it actually wouldn't work for the drama portion of the game. It would imply that the player is able to combat the darkness directly which is not the feeling I want the player to have. The personality of the "curse" is that there is an intelligence behind the rage and that it can only be satiated by killing. Therefore, the curse is that the player will never lose the urge to kill after raging until a death has resulted. The death has to be inevitable for it to fit into the story properly.

I was more thinking along the lines of what occurs in Heavy Rain in "stressful situations": ... But does that sound like an acceptable mode of delivery for a player response opportunity?

Aah, I see. I'll confess that I haven't played Heavy Rain, so I haven't tried that myself, but I could see it working. I will leave a caution that interfering with the interface can, if not handled well, lead to player frustration towards the game: it can feel as though the game is interfering with your attempt to act, rather than that you're making a mistake.

games are a more interactive experience. Would your evaluation account for that?
...
It would be more of a representation of how the character is at the mercy of this curse. It doesn't really do anything to connect the player to it.

I will leave a caution that interfering with the interface can, if not handled well, lead to player frustration towards the game

I feel like you guys are both concerned about the effect of temporary interface distortion, but I can testify that, from my own experience, it was in fact a highly effective technique for engaging me with the narrative scenario. The moments in which this technique was employed were by far the most intense and permeating experience in the game (in the sense of permeating the boundary between player and avatar). But I definitely agree, it all has to do with how intense the distortion is made. If it's too fast, it will be felt to be too irritating and impossible to deal with. Too slow would just make it an unnecessary annoyance.

I do think that it might be a good idea to have instances where the player uses directional controls to "combat" the, for lack of a better phrase, "motor manipulations of the body" paired with a zoom-in effect as Thaumaturge suggested earlier on (this is actually quite similar to the evolved techniques in Quantum Dream's second game Beyond: Two Souls).

Perhaps the combination of these techniques (though likely not at once), will be effective at generating the aesthetics I'm looking for.

Please let me know if you guys think of anything else as the Heavy Rain example was all I could really think of beforehand. Thanks for the help.