How to save time in this game.

For Any%

Platform tutorial 1: There is a trick you can do to save a few seconds. Start mashing right and up as the tutorial is loading, and you'll start breaking the block early.

Platform tutorial 2: You can use the same trick to start jumping on the first block to the right in advance. You can also completely skip this tutorial by going left right away, which saves about 6 seconds, but this is not necessarily recommended because you will not unlock the jetpack in doing so. The jetpack makes it much easier to quick-kill bosses, especially the last two.

Shop tutorial and cutscene: Mash the escape key and you can skip the shop tutorial quickly, then hit up a few times and enter to start the main game.

Main game: During the autoscroller segments, you're not really going to save time. Focus on getting powerups which will help you quick kill the bosses. You do, however, want to make sure you are going fast enough in the autoscroll segments so that you can at least trigger the boss the second it becomes available. You can feel free to take a single one up mushroom as a safety net. If you still have it after the final boss, you won't lose any time wasting the one up mushroom while he is dying. More than one would probably be a time loss though.

First boss: You want to get the plant boss, as you can just spam jump on it five times. There's also a difficult trick you can do sometimes with the plant boss. If you hit him at the right time while he's falling down to start the fight, he will sometimes slide off the bridge into the lava, instantly killing it and saving you a few seconds. This is inconsistent though. The bird can also be quick killed, but it's slower by a few seconds. You will probably need at least one powerup to survive either. 

Second boss: The cloud boss can probably be more consistantly killed faster than the other one if you have powerups that let you get above the cloud boss right away, and you can afford to lose a few powerups. If you get the other boss, you want it to start out as high as possible so you can get a bunch of hits on it before it sinks below the bridge.

Third boss: Always the chicken commander, his reaction to being hit each time can be really good for you, or he can be a jerk and fly out of your reach. Just hope for the best and try to bring powerups like the jetpack and double jump into the fight. 

Final boss: Always the great wizard ohe. Pretty straight forward, you won't need any powerups or one up mushrooms after you kill him, so just go completely ham on him. Clear up enemies when he's swapping phases. Right after you beat his first phase, make sure you are on the ground near him so that he will quickly swap to phase 2 without having to get close to you. Try to maintain a chain of consistent hits bouncing on top of him while he's flying. Brick RNG can be a pain in his final phase, don't let yourself get crushed if you don't have a one up mushroom. After killing him, make sure you waste your 1 up mushroom(s) while he's dying. Don't die too quickly on your final life, wait for the achievements to pop up before dying again, otherwise the cutscene might not trigger, and the run won't count.

For 100%

Here is a simplified list of what you need to do.

1. Beat the 'final boss' (the wizard) three times. This will cover all of the first through third boss achievements as well.
2. Fall in lava 50 times (probably best to get this at the end of the run).
3. Get a 'surf' combo of 22.
4. Max out each type of follower at least once, besides the 1-up mushroom (You don't have to max out all 3 of them in the same game).
5. Use the climbing gloves 15 times total across your runs.
6. Complete 45 missions/challenges.
7.Win two double boss battles.
8. Kill 50 dragons across multiple games.
9. Reach 3,000 feet (optimally, you'll complete this and the two double bosses in the same run).
10. Get 10,000 coins in the bank (this includes spent coins). This is what you'll want to focus on once you have the more skill based achievements out of the way, like defeating the boss 3 times, the 3,000 foot achievement, and the double bosses. It's up to you how you want to go about this, but I was trying to multitask the 45 missions quest with this to the point where I would restart a run as soon as I completed all the current quests I had. Might get you more coins faster completing extra missions than just getting a high score each run, but I'm unsure.