A drama is a shape you can feel: a slow setup, a climb, one high turning point, then the fall to an ending. Gustav Freytag drew it as a pyramid in 1863, and it still frames every screenplay. Walk the story (or tap) and watch the tension crest and break.
Freytag's dramatic arc (Die Technik des Dramas, 1863). Five stages: EXPOSITION (the setup), RISING ACTION (complication builds), CLIMAX (the single turning point — the peak of tension), FALLING ACTION (consequences unfold), and DÉNOUEMENT / catastrophe (resolution). Tension rises to exactly ONE maximum at the climax (Freytag placed it past the middle, near ~62%) and falls after — an asymmetric peak, not a symmetric hill. The tension(position) curve and the current stage are computed live. A fail-loud self-check throws unless the curve has a single maximum located at the climax and the five stages partition the story.
A single-peak model with the climax at a fixed ~62% (Freytag analysed five-act tragedy; modern three-act and TV structures place turns differently). The single-maximum property and the stage boundaries are exact.