This is a really nice polished game that fits into the theme well - love the simple graphics, which can be a bit of a problem if the other elements of the game don't hold together well. The random element of the dangers/bonuses changing every 13 seconds makes it interesting for multiple playthroughs and it seems balanced to give challenge but allow improvement - the different elements stop it from becoming too dull. Perhaps you could experiment with grouping the randomness by difficulty to give advancing difficulty but that might destroy the feel of what is a great arcade-style game - well done.