My superhero system

Summary: Strongly borrowed from The Pool, Redline and Donjon.

Tone: Contemporary heroic, wild stuff.

The rules: Every roll uses 6d6. 1-3 is a failure, 4-6 is a success.
Either the PC or the GM can call for a roll:

Desired Effect # Success Dice #XP Dice
Epic! 1 5
Huge 2 4
Great 3 3
Major 4 2
Minor 5 1
The number of success only matter for the XP dice
If you succeed, you can take the victory, or can roll for a greater effect if desired (up 1 effect rank). This is "raising the stakes."
If you fail you can spend an XP to reroll the 6d6.
Your actions always always start at the lowest effect. *But to make plot-irrelevant actions faster, the GM can just declare a Great roll instead of having you build up your action.

Examples of play:
-A kid falls off a tree and you try to catch him. The GM decides it would take a Minor effect to do this.
Roll: 1,2,5,5,6 and 1
You succeed catching the kid, but get no XP for it.

-A bus is speeding out of control. The GM decides it would take a Major effect to stop it safely.
Roll: 1,2,3,3,3 and 1
You failed this roll, but spend an XP to reroll:
Roll: 1,3,4,4,5 and 6
You succeed, you increase your effect:
Roll: 1,3,4,4 and 1,6
You narrate your success and gain 1 XP.

System notes: The GM should probably narrate the failures.
If a person needs a Great action, but wimps out and stays with a Major success, the GM may decide to narrate a partial success.
If a player wants to declare an action, he may stop rolling whenever he wants. However, the GM may "cap" actions. This is meant to stop overzealous players from making unauthorized insane changes to the adventure, like making the moon crashing into the earth for no reason. The moon crashing may be an Epic action, but the GM can rule that PCs are only allowed Great actions for this part of the adventure.
I just realized that how actions are "built up" copies directly from Donjon's magic system.

Combat: Simultaneous, 1 "round." Both players start with Minor actions. Double successes means the players both advance to a greater action. Keep going until one person fails. The winner gets the action and the XP reward. If there are double failures, combat can either end in a draw or the fighters can start up another fight.
NPC combatants should have a "level." Ie. to beat a minor nemesis, the PC will not win unless he gets a Great victory.
If there are multiple combatants, as each combatant fails, the other fighters can narrate what happens to him.


Issues: I hope that was clear.
The 50% success on each die might be too lenient.
Anything else?
I'll post the setting material stuff soon, but I welcome all suggestions.