There is a supernatural being who created everything we know. His nature is pure love, which governs the universe. We were created to exist in loving relationship with God and each other, to love and be loved. Our ancestors rebelled against love and, as a result, Earth is now the theater of a war between love and selfishness, personified by God and Satan. To win the war through a demonstration of love's superiority, God allowed His Son, Jesus, to die on our behalf, pay for our rebellion, and restore us to loving relationship with Him. If we repent from our rebellion and accept Jesus as our savior, we are restored to our purpose: loving relationship.
Salvation is available to everyone who accepts the love God is offering all of us. We are afforded legal justification for our rebellion and eternal life.
Existing in loving relationship with God is transformational, not just in a spiritual and religious sense, but also in our daily lives. Relationship with God is the solution to all ills and problems. We don't need twelve rules for life; we only need one. Relationship with God is the only cure-all there is, but it works every time--though perhaps not as we mean it to.
We can live in harmony with our design, or at odds with it. For instance, the human body is designed for outdoor movement. Yet, we have designed our civilization around indoor sitting. No wonder we are plagued by physical and mental disease.
Being designed means that the naturalistic fallacy is no fallacy at all, except insofar as our design has been corrupted by rebellion against God.
Morality is defined by our motives, not our actions:
And if I give all my possessions to feed the poor, and if I surrender my body to be burned, but do not have love, it profits me nothing. - 1 Corinthians 13:3
Christian transformation results in being motivated by love rather than selfishness.