What opens the lower grid?

The green and purple feeds first lower the top 10 counter; the middle shelf marked 5 must then open before the lower grid can be filled safely.

Why keep red on the right?

The right pocket is the only clear landing area for the final red bars after the central divider is exposed.

Sand Blocks level guide

expert 5 colors

Level 290 drains the top 10 shutter with green/purple, opens shelf 5, and delays the right-half red bars until the fixed divider clears.

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Place green L from tube 1 at r2-r3,c1-c2, purple horizontal at r2c3-r2c4, and blue 1x2 from tube 3 at r2c6-r2c7; keep divider c4 and r3-r6 clear.
Feed green and purple alternately until the white shutter changes 10→8→6; leave red pocket r4c6-r4c7 empty.
Move blue vertical to c7,r3-r5, then pink corner to r4c1-r5c2; let top counter reach 3→1 before touching shelf 5.
When top shutter reaches 0, slide blue bars to r4c5-r4c6 and r5c5-r5c6, then green L to r6-r7,c1-c2; shelf 5 remains closed.
Reduce shelf 5 with red 1x2 at r4c6-r4c7 and blue horizontal at r5c2-r5c4, confirming 5→3→2; keep purple destination r6-r7,c5-c6 clear.
Once shelf 5 opens at 0, move purple 2x2 through c4 into r6-r7,c5-c6, then pink vertical to c4,r6-r7; verify both 100%.
Finish red corner at r3c6-r4c7 and red bars at r8c1-r8c3 and r8c5-r8c7; place final blue vertical at c7,r6-r8 and wait for empty state.

Colors in this level:

Green, Purple, Blue, Red, Pink

Parking a red bar across the middle shelf while the blue feed is still active.
Moving the large purple rectangle into the central divider before the 5 shelf opens.
Filling the right pocket before the top 10 counter reaches zero.

Board notes 5 details

Layout: Three top tubes supply green, purple, and blue sand; a white shutter marked 1/10 spans the top and a middle shelf is marked 5. Red, blue, pink, purple, and green receivers surround a fixed central divider.
Goal: Drain green and purple to lower the top 10 counter, open the middle 5 shelf, and reserve the right half for red and blue after the divider clears.
Opening: Catch the green L under the left tube, stage the purple bar, and place the blue upper receiver without covering the central divider.
Danger Zone: A red bar across the middle shelf blocks the blue feed; moving the large purple rectangle into the divider before the 5 shelf opens traps its feed.
Mechanics: Three independent feeds, a 10-to-zero horizontal shutter, a second 5 counter shelf, and a late red/blue lower-grid finish are evidenced.

What opens the lower grid?
The green and purple feeds first lower the top 10 counter; the middle shelf marked 5 must then open before the lower grid can be filled safely.
Why keep red on the right?
The right pocket is the only clear landing area for the final red bars after the central divider is exposed.