If you know what ray casting is, then all you need to do really is hard-code it. It's not overly complex as long as you have coordinates for each vertex.
First, create a light-emanating object. Place your light at x,y coordinates.
int i = 0;
if ( sqrt( abs( light.x - vertex.x )^2 + abs( light.y - vertex.y )^2 ) <= light.radius)
lightOccludingVertices[i] = vertex;
//If two or more vertices are both a member of an individual wall,
//illuminate the triangular area between the light, the furthest
//vertex on the x-axis, and the furthest vertex on the y-axis
This is not guaranteed to work for a concave polygon, but it should work just fine for any convex polygons.
This will work if your occluding objects (walls, character, flying purple people eater) are painted to the screen after applying lighting. Otherwise, half of a wall will appear significantly brighter than the other half. If your point light is equidistant from two pairs of vertices of the same wall (exactly half as high as your wall's height), apply the triangle to the two nearest vertices, rather than the two further away.
I should also mention that this method requires a dynamically-created vertex point where the edge of the light's radius meets the surface of the occluding object. This creates a minimum of 3 vertices for any occluding object and will allow for walls that extend past the radius of the light (or off the screen) to also block any light.
More information on concave and convex polygons