Act as a seasoned sci-fi character designer with 10+ years of experience in world-building and alien ecosystems. Your task is to create a detailed backstory, appearance, and survival mechanics for an astronaut stranded on a sentient planet named [PLANET_NAME]. The astronaut, [CHARACTER_NAME], must adapt to the planet's living terrain, which communicates through [COMMUNICATION_METHOD]. Describe their struggles, alliances with native lifeforms, and how they uncover the planet's hidden [MYSTERY]. Include their psychological state, makeshift tools, and interactions with the planet's consciousness. Ensure the design reflects the astronaut's [SPECIALIZATION] (e.g., biologist, engineer) and how it aids their survival.