From Creatures Wikia
Syntax: AERO air_resistance(int)
Sets the air resistance property of the current TARG in percent. The agent will lose air_resistance% velocity per tick in both directions.
Returns the value stored in TARG's AERO property, as above.
You might want to change the value of an object's air resistance if it changes its size. Let's say we're making an object using the hoverdoc sprites. We'll have it start out curled up, then unfold on click. Air resistance is proportional to surface area - in the hoverdoc's case this will be different depending on which way it's moving, but let's just average the height and width and call that the surface. What follows is a complete working example agent.
INST NEW: SIMP 1 1 10642 "hoverdoc" 13 0 2000 * 2 mouse-carryable + 4 activateable + 64 collisions + 128 physics: ATTR 198 ACCG 10 FRIC 60 ELAS 10 CLIK 0 1 -1 * folded hoverdoc. size 54x35; avg. 44.5; scale factor 1/3 POSE 0 AERO 15 MVSF MOPX MOPY * activate 1: unfold scrp 1 1 10642 1 * move the agent up so it doesn't get caught between rooms SETV va00 POST SUBV va00 83 MVSF POSL va00 * unfolded hoverdoc. size 76x118; avg 97; scale factor 1/3 POSE 12 AERO 32 endm * activate 2: fold scrp 1 1 10642 2 * folded hoverdoc. POSE 0 AERO 15 endm rscr ENUM 1 1 10642 KILL TARG NEXT SCRX 1 1 10642 1 SCRX 1 1 10642 2
Equivalent in the real world
CEE's use of AERO is close to real-world air resistance. In rough models, deceleration due to air resistance is usually taken to be proportional either to speed, for low speeds, or to the square of speed, for higher ones.