Less simple

• Less cushiony
• More difficult
• "Pull more!"
• Less giving
• More callous
• More demanding
• Like topaz vis-à-vis quartz
• Requiring more effort

WordNet Word definitions in WordNet
adj. not easy; requiring great physical or mental effort to accomplish or comprehend or endure; "a difficult task"; "nesting places on the cliffs are difficult of access"; "difficult times"; "a difficult child"; "found himself in a difficult situation"; ...