An invisible debt grows every night, which you pay back with interest during the day.

What calls its own name from the treetops, but lets others warm and feed its only offspring? Solve the riddle → What was once criticized as an ugly construction, but is now an iron monument that breathes with the seasons? Solve the riddle → I am a colorful kingdom beneath the sea, built by tiny animals yet larger than many cities. What am I? Solve the riddle → What stretches like a spine across an entire continent, yet has neither life nor limbs? Solve the riddle → Your internal army fights invisible invaders, without your command, day and night. Solve the riddle →