Time Traveler's Regret Panel

A single dramatic comic panel of a lone scientist standing in a glowing time-machine chamber, watching a holographic memory of a moment he can't change. Detailed sci-fi lineart, cool cyan and violet glow, screentone gradients, subtle particle effects swirling around him. A caption box reads 'Some doors, once open, cannot be closed.' Somber expression, dramatic backlight, emotionally heavy cinematic sci-fi mood.