God of Thunder is an old DOS game, made by Ron Davis (Software Creations) and released in USA in 1993. It's an action-adventure game with top-down view, similar in ways to The Legend of Zelda. It was originally a shareware game in three episodes, the first being available for free, but now it's entirely freeware, and you can get it at the
Adept Software website.
You're Thor, the namesake of the game, and you're commanded by your father Odin to complete several missions. The game has you explore fields infested with enemies, some of which recognisable as part of the Norse mythology; you'll have to find your way through plains, towns, caves, and puzzles of all sorts.
The game isn't too hard, since you restart at the entrance of an area if you die (and you will die, a lot), but there are many instant-death traps (some of which reminiscent of Lolo, for those who know). However, certain block-pushing puzzles can leave you stumped, in which case I'd suggest you take a look at
GameFAQs.
Direct link to game download