The counter reads joints, not pixels. If the joints it needs are in the frame, lit, and not cut off at the edge, it counts. Everything below follows from which joints each exercise uses.
Push-ups: one metre, in front, phone upright
Stand the phone upright about a metre in front of your hands, screen towards you. Lean it against a wall, a bottle or a book. The counter needs your head, shoulders, elbows and wrists. It measures how far your arm folds and how much wider your shoulders look as you come down, so it must see you from the front, not from the side.
Too close is the usual mistake. When the phone is right at your hands, the elbows leave the frame at the bottom of the rep, and the app stops counting without a clear reason. The checklist before the set flags this: if it says you are too close, move the phone back half a metre, not yourself.
Squats: two metres, in front, whole body
The squat counter measures hip height above the feet and how much shorter the whole figure gets. It needs shoulders, hips, knees and ankles in the frame, which means the phone has to be about two metres away and you have to face it. A hallway or a doorway is enough.
Turning sideways breaks it. From the side your shoulders overlap and the height reading jumps; the app tells you to turn back before it counts anything. Raised arms are fine.
Crunches: phone at your side, on the floor
Lie on your back with knees bent and put the phone on the floor about a metre and a half to your side, screen towards you. The counter reads the angle between torso and thighs and how close the shoulders get to the knees, so it needs a side view of head, shoulders, hips and knees.
The app turns the camera image a quarter turn on its own, because the pose model is trained on standing people and sees a lying person badly. You do not need to do anything for that; just keep the phone on its side on the floor.
Plank: phone at your side, from the waist
Same placement as crunches: on the floor, a metre and a half to your side. The plank is judged on the line from shoulder to hip to knee, on forearms lying on the floor, and on the hips staying still. From the front a plank and lying on your stomach look the same, which is why the app refuses the front view for this one.
Lowering your head does not break the hold. Letting the hips sink does.
Light
The camera needs to see you, and a pose model needs edges: a lit body on a plainer background. A lamp behind the phone, pointing at you, works. A window behind you makes you a silhouette, and the model loses the elbows first. A dark room gives you a checklist that never turns green rather than wrong counts.
What the checklist means
Before every set the app shows which joints it can see and whether the distance is right. It waits until all of them are green, then measures your top position and starts counting. If a joint goes grey during the set, the count pauses and the reason is written on the screen. Fixing the placement is always the right move; the counter never guesses where a hidden joint is.
Once the phone is in place, the push-up counter takes over: every rep it counts lands as a hit on the monster in front of you.
