Generate a serene and detailed illustration of a Japanese Zen garden, capturing its tranquil and meditative essence. The design should feature classic elements such as meticulously raked sand or gravel, carefully placed rocks, simple water features, and perhaps a distant view of mountains or minimalist vegetation. The artwork should allow for coloring space that encourages mindfulness and relaxation, with clear, monochromatic lines suitable for easy coloring. Include a subtle area within the garden or at its edge for a mindfulness quote to be added later. Ensure the design is perfectly centered within an 8.5x8.5 inch square, with high-resolution and clear lines for printing in PNG format