Controls (1D Mode): L = Accelerate (+x) | J = Accelerate (-x).
(In 2D Mode: I/K rotate ship, J/L apply thrust forward/backward).
F = Fire Laser | S = Instant Stop | P = Pause/Unpause.

Calculus Focus: Notice that when velocity and acceleration have the same sign, the ship's speed increases ("accelerating"). When velocity and acceleration have opposite signs, the ship's speed decreases ("decelerating").