Pretty sharp game
I love Tyrian to death, so any homage to it is fine (after all, the Metal Slug clones consistently get good scores). This is a really good games with very nice graphics, gameplay, and a reasonable story too (something you don't see often in arcade-esque games.)
Some points to note
-A difficulty option; it does start off a bit harsh, but after the first level with a few upgrades and getting used to patterns, it gets much much easier (the irony of the first level being the hardest).
-Passwords; pasting code is annoying, I had to cut and paste something else and lost the HTML to return where I was.
-Higher Gem Spawning; gems are a bit short to come by, I'd like to be at or near full upgrades by the end of the game. I felt like I had barely gotten anything by the time I was in the final stage.
-Upgrades; I'd like to see more variety in the menu, perhaps alternate weapons to switch to for more strategy. While I do enjoy the classic, basic weaponry as opposed to the "giant lasers that rip apart half of the screen", most would enjoy some upgrades to lean towards those huge weapons later on in the game at least.
All in all, a great game with a lot of good points and just a few things that could make a sequel potentially one of the best vertical shooters around. Kudos again and I hope to see more from you in the future.