This app was mentioned in 1 comment, with an average of 1.00 upvote
Not sure if these were ever browser games, but it sounds a lot like one of these Android games. Maybe one was based on the browser game?
https://play.google.com/store/apps/details?id=com.gotow.hexdefense&hl=en
https://play.google.com/store/apps/details?id=air.air.TwinPixel.LaserDefense