The Four Forces
Weight pulls the aeroplane towards the ground, and it is the one force that never changes during a flight. A loaded aircraft is heavier and a lighter one is lighter, but you cannot alter either in the air. Whatever you took off with is what you have to fly with.
Lift is the wing pushing back, upwards, roughly in proportion to how fast the wing is moving through the air and how steeply it is angled into the wind. It is the counterweight to weight, and it is not free.
Thrust is the engine pulling the aeroplane forward. Drag is the air refusing to get out of the way. Thrust and drag fight each other along the direction of flight, and lift and weight fight each other across it.
In steady level flight the two pairs are in balance, which is a much rarer state than it sounds. The aeroplane is not being held up by the engine. It is being held up by the wings, and the engine is only there to keep the wings moving fast enough to do it. Take the engine away and the aeroplane does not fall out of the sky, it becomes a glider, which is a perfectly good way to fly and the entire subject of one of the games here. What it cannot do is stay level without spending height to pay for the speed that drag is eating.
Only Two of Them Are Yours
A pilot has direct control over thrust, by moving the throttle, and indirect control over lift, by changing the angle of the wing. Everything else is a consequence. Nobody controls drag. You can only make it worse, and you do so every time you increase lift.
That coupling is the whole subject. Lift and drag rise and fall together. Angle the wing up to make more lift and you also make more drag, which costs you speed, which reduces your lift again. The aeroplane settles into a balance point rather than obeying an instruction.
Which is why a game like Drop is entirely about one decision. You get a single steer and a landing spot, and everything between them is these four forces settling out without asking you.
What a Stall Is
Past a certain angle, the air stops following the curve of the wing and starts tearing away from it instead. Lift collapses. This is a stall, and the important thing about it is that it has nothing to do with speed.
It is possible to stall at any speed and any attitude. Pull hard enough at two hundred knots and the wing lets go. What matters is the angle rather than the airspeed, and this is why pilots talk about angle of attack the way drivers talk about the rev counter.
The recovery is the least intuitive action available: push the nose forward, and give up height to get the wing working again. Trading the thing you wanted, altitude, to buy back the thing you need, attached airflow.
What the Controls Actually Move
There are three moving surfaces on a conventional aeroplane and each one rotates the aircraft about a different axis. The elevator on the tail pitches the nose up and down. The ailerons on the wings roll it left and right. The rudder yaws it, swinging the nose sideways without banking the wings.
A turn is not one of these. A turn is a roll followed by a pitch, and the pitch is the part people forget. Bank the aeroplane and the lift stops pointing straight up, so it stops holding the aircraft up as effectively as it was. To hold height in a bank you have to pull back and make more lift, and more lift costs more drag, so the aeroplane slows down. Every turn costs speed. There is no turn that does not.
That is the part that turns flying from a set of directions into a set of trade-offs, and it is why a game can be built out of two keys. If banking left merely moved the aeroplane left, a game about flying would be a game about steering, which is not interesting. Because banking left costs energy, a game about flying is a game about deciding when to spend it.
The throttle is worth being precise about as well, because it does not do what a car pedal does. Opening the throttle adds thrust, and thrust only has to beat drag. In level flight, opening the throttle makes the aeroplane go faster until the extra drag catches up. Point the nose up and the same throttle setting makes it climb instead, at the same speed. The throttle sets how much energy is going in. What you do with the nose decides whether that energy becomes height or speed.
Why This Makes a Good Game
A four force model is interesting to play with because it refuses to let you have one thing without paying for another. Speed costs fuel. Height costs speed. Lift costs drag. Every control in the aircraft is attached to something you wanted to keep.
Game Rig uses that model rather than a physics engine. Glide has no engine at all, so thrust is zero and the only way to stay up is to find lift somewhere else. Dogfight makes height and speed the same currency, so spending one spends the other. In both cases the difficulty is not in the controls, which are two directions, but in the trades.