Super Time Force Ultra could have been amazing instead of just great if it knew what it wanted to be and focused on one aspect of the game. As it is, it's kind of a mess to play, quite bad with the keyboard and only made a little bit better by the use of a controller - something I try to do as little as possible with PC games - and while there are a few design decisions here and there that I find just weird, I had a great time with it and I think it's a charming game most people should try.
The basic concept of the game is a 2D sidescrolling shooter where you have a set number of lives and you can rewind time and replay parts - or whole levels - using these lives. By doing so, you can finish objective faster - killing a boss twice as fast - save your previous lives - by killing enemies that killed you before they do so - or solve puzzles - like breaking two switches at the same time. You have a limited time of 60 seconds to go through stages - although you pick up 10 second bonuses along the way - and you unlock various characters with two attacks, one basic and one charge up.
One of the first flaw I have with the game is this very system. It's annoying that you have to deal with this whole two attacks system, for all but one characters, I always used the charged-up attack and only one of them I mashed the attack button repeatedly to progress. There should only be one attack per character and it should be auto-fire. If the game really needed special abilities, it could have been mapped to another button. The characters range from a 3-way spread guy, a lady with a bouncing laser, grenades/rockets character, someone with a shield, and a bunch of other people.
The game doesn't motivate you to use different characters. I've spend about 80% of the game using the 3-way spreadgun guy, and maybe 15% bouncing laser and the last 5% were times where I tried to be fancy and use the shield character to protect the rest of my team. There are no real spots where you 'need' to use a certain character. No walls that can only be destroyed by rockets, no bosses have attacks so massive that you 'need' to use the shield character, and don't get me started on Saxton Hale, that girl with boomerangs or the guy with the light saber. They add flavor for sure, but when you're concerned with just beating the game, some characters just work better. Also, when you save a character from dying, you get an additional hit point and the charged-up ability of that character gets added to yours. Maybe it would've been cool to be able to stack more than one bonus HP, either that or getting the basic attack as well - see my previous idea about getting rid of the two moves.
The bosses are pretty cool and this game features a few fights where you have to protect something while defeating everything else, but it's mostly always the same pattern of finding what works and then throwing about 15 guys with spreadguns into the fight, winning any battle. You only have 60 seconds, but if you retry from the start with more guys, of course you're going to win the fight faster. I also wish the firing controls were better, you shoot in the direction that you're moving in, so to fire in diagonals - something neat with bouncing lasers - you have to move in a specific way. Twin stick controls might have worked better.
To conclude, STFU is an awesome little game that has it's issues but is mostly redeemed by its style and the way you can brute-force almost everything even if you're not great at shooting and platforming. Just don't expect the puzzles to be too clever and the shooting to be super tight and you'll be okay.