The President of Costa Rica is elected using a modified two-round system in which a candidate must receive at least 40% of the vote to win in the first round; if no candidate wins in the first round, a runoff will be held between the two candidates with the biggest quantity of votes.

The 57 members of the Legislative Assembly are elected using closed list proportional representation through the largest remainder method from seven multi-member constituencies with between four and 19 seats, which are based on the seven provinces.

Sources and Further Reading:

http://blog.politics.ox.ac.uk/a-trump-in-the-tropics-why-a-demagogue-became-the-leading-contender-in-costa-ricas-and-what-this-means-for-the-upcoming-election/

Costa Rica: Presidential campaigns get underway

http://country.eiu.com/article.aspx?articleid=1696096753&Country=Costa%20Rica&topic=Politics