Why does Smash Fest Level 70 want the top-left corner first?

Because that corner creates the first staircase in the board. Once it opens, the right rectangle loses support and the cleanup becomes much smaller.

Smash Fest! level guide

Smash Fest! Level 70 Walkthrough

hard Target: 18 moves 5 colors

Smash Fest Level 70 is a staggered checker wall that clears best when the upper-left corner is opened first, because the board then steps down into a much smaller right-side cleanup.

Board Notes

Layout: A staggered orange-and-blue wall is cut by several white striped bands and ends in a tall right rectangle. After the upper-left corner opens, the face becomes a staircase instead of a full checkerboard.
Goal: You need to break the upper-left corner first, turn the wall into a staircase, and then clear the late right rectangle plus the short base strip with the last red-dot cube.
Opening: Start on the upper-left corner so the face stops behaving like one full checkerboard.
Danger Zone: Firing straight through the middle leaves the upper-left corner intact and keeps the right rectangle too well supported for a cheap cleanup.
Mechanics: This is a staircase-conversion board where one top-left opening transforms a dense checker wall into a lower step-down solve with a single late right block.

Quick Tips for Smash Fest! Level 70 (spoiler-free)

If the board still looks like a full rectangle, keep opening the top-left notch; the clean route is the one that turns the wall into steps.
With 5 colors in play, clear the pair with the fewest blockers first so the board opens up instead of tightening.
Think in chain clears. The best move is the one that sets up the next two moves, not just the quickest current match.

How to Solve Smash Fest! Level 70 — Full Solution

Shoot the upper-left corner instead of the middle striped band.
Keep widening that notch until the left side drops and the wall starts stepping down.
Let the loose left pieces fall so the short base strip becomes visible.
Remove the exposed middle leftovers and the striped pieces across the lower shelf.
Cut down the remaining center-right support after the wall has already narrowed.
Work on the tall right rectangle once it becomes the only real height left.
Finish the last red-dot cube and low orange blocks still resting on the base strip.

Colors in this level:

Orange, Blue, White, Red, Yellow

Common Mistakes to Avoid

Drilling the middle stripes while the upper-left corner of the wall is still sealed.

Frequently Asked Questions

Why does Smash Fest Level 70 want the top-left corner first?
Because that corner creates the first staircase in the board. Once it opens, the right rectangle loses support and the cleanup becomes much smaller.