2] As an author full of ideas, what would you do to make us laugh like fools or cry like little girls? Would you work especially on the narration ? Interaction ? Visuals ?

Don't force the humor, let it come out of context of the player's actions, and whenever possible, make that humor reactive based on the player's actions, not on watching a passive sequence. Try to get inside the player's head, and not only anticipate what they may think, but provide options for it. As an example, nothing created a more sympathetic reaction for me than Ripley in Aliens echoing exactly what the viewer is thinking ("Nuke 'em from orbit." Followed by "They can bill me.") - everyone in the audience can completely sympathize with getting the hell off of LV-426 and dropping nukes on a nest of vicious predators with acid for blood. So look for points in the game where you catch yourself thinking of a solution and have characters in the game echo what the player might be thinking.

Narration, interaction, and visuals can all contribute to humor or sense of loss, but really, you want to focus on the audio.

The tone of a voice actor and the background music will do more to create mood than any visual or interaction sequence can strive for. As an example, in Alpha Protocol, Michael Thorton can develop a romance or a hatred with a contact, Madison, in the game... and when you interact with Madison, the music and the voice acting is what drives the emotion of the scene. When you have a hatred going, the music is tense, dangerous, and everything about Madison's tone tells you how much she despises you. On the counterbalance, the voices and music (softer, slower) is what drives home the romance at the other end of the spectrum.​