1: If you see a weird block like slim green portal it will turn you mini. it basically shrinks your icon
2: If you see a weird block like slim purple portal it will turn you back to regular size
3: If you see a orange portal that somewhat looks like a tip of an arrow, it will duplicate you. the clone will have inverted gravity and both jump when you click
4: If you see a blue portal that somewhat looks like a tip of an arrow, it will get rid of your clone
5: if you see a big black portal with a blue edge on the left, it will teleport you to a big black portal with an orange edge.
6: If you see a cool looking blue orb that isnt circular, it acts like those teleport portals, but you have to click on them for it to work.
7: if you see a big orange arrow facing the left, it will put you on 0.5x speed
8: If you see a big blue arrow facing the right, it will put you at 1x speed (normal speed)
9: If you see two big green arrows right next to each-other that are facing to the right, it will put you on 2x speed.
10: If you see three big pink arrows right next to each-other that are facing to the right, it will put you on 3x speed.
11: If you see four big red arrows right next to each-other that are facing to the right, it will put you on 4x speed.
12: if you see a floating pickup thing (hearts, skulls, keys, potions, etc) it will activate a random trigger
13: if you see a big yellow coin with a Star on it, its a secret coin, use it to unlock stuff
14: if you see a big silver coin with a C on it, its a user coin, use it to unlock stuff
15: if you see a big bronze coin with a C on it, its an unverified user coin, its useless.
16: If you see creatures, they act like spikes, avoid them.
17: If you see saws/gears they act like spikes, avoid them.
18: if you see half blocks, they are just like blocks but with a smaller hitbox.

If you see anything else its likely decoration and doesnt do anything. or i just forgot something.