Artificial Life ENvironment (ALIEN) is an artificial life simulation tool based on a 2D particle engine specialized in CUDA for soft bodies and fluids. Each simulated body consists of a particle network that can be equipped with high-level functions, ranging from information processing capabilities to physical equipment (sensors, muscles, weapons, constructors, etc.), whose execution is orchestrated by neural networks. The bodies can be considered as agents or digital organisms operating in a common environment. Their construction blueprints can be stored in genomes and transmitted to offspring. The simulation code is written entirely in CUDA and optimized for large-scale real-time simulations with millions of particles.