/* for mobile 寬最大800 */
@import url(c.css) (max-width: 800px);

/* 寬最小801，最大1000 */
@import url(d.css) (min-width: 801px) and (max-width: 1000px);

/* 寬最小1001，最大1600 */
@import url(a.css) (min-width: 1001px) and (max-width: 1680px);

/* 寬1681以上 */
@import url(b.css) (min-width: 1681px);