Sand Loop

Sand Loop is an original falling-sand scheduling puzzle. A packed sand mosaic becomes a moving stream: send colored cups onto a looping conveyor, let exposed matching sand tumble down, and collect every last grain without blocking the available slots.

The picture and its colored background are both real sand filling the tray. A closed floor supports the packed grains; cups open matching bottom gates, and gravity fills the resulting gaps. Colors retain their identity, grains occupy real grid cells, and cups only fill when sand reaches them. It is an original interpretation of the sand-sorting idea, not a claim to reproduce another game’s hidden rules.

1. Look along the picture’s lower edge to find colors that can flow.
2. All cups form a fixed arrangement. The top is open; the left, right and bottom edges are solid walls. Select a colored cup touching the top opening or an empty tile connected to it. Other cups show question marks and stay blocked. Stone pegs and dividers obstruct the route. Send a star or heart key cup to open its matching gate; the key cup still uses a belt slot. Cup-seal gates from level 31 open only after their marked cup reaches 100%.
3. The cup springs from its tile onto the moving loop, leaving an empty cell. Lower sand starts flowing; unsupported upper colors follow, collide and mix. A cup catches sand only as its mouth passes beneath the floor gates.
4. A full cup leaves and frees its slot. From level 41, split cups collect two colors in separate halves: both percentages must reach 100% before their shared slot is free. Reach 100% collection to finish immediately, without waiting for the last cup to leave; a full loop only loses when all collection is blocked.

On a computer

Click a waiting cup, or use Tab and Enter or Space. Open the in-frame path map to replay unlocked levels. Complete every earlier level before entering the next one; shared level URLs follow the same rule. Use the in-frame tools without navigating away.

On a phone or tablet

Tap an exposed outer cup. Sliding a finger cancels that tap so scrolling does not accidentally choose a container.

Game Features

• One hundred original sand pictures. Levels 21–30 introduce Two Paths: choose either key first and plan which pocket to clear.
• Levels 31-40 add Fill to Open: marked cup seals unlock only at 100%, with one-time teaching and live gate percentages. Levels 41-50 add Split Cups: two independent colors share one cup and one slot; fill both halves to make it leave. Levels 51-60 add Linked Cups: expose both golden-linked partners and keep two slots free to send either one; each full cup leaves independently. Levels 61-70 add Color Switch: fill the first color to100%, then catch the next color using the same slot. Both stages must finish before a switch cup leaves. Levels 71–80 introduce Double Lock Gates: both marked cups must actually reach 100% before their shared gate opens. Save room for the lower sand color that lets the second key fill. Later pictures combine separate star and heart pockets with split, color-switch or linked cups. Levels 81–90 add Ice Passages: fill the entire snowflake cup to melt a blocked ice tile into a real empty path. Levels 91–100 add Color Stamp Locks: fill any whole cup of each of the three colors shown on a lock. Duplicate colors count once; split and color-switch cups contribute both original colors only when every part finishes. Five vivid colors with optional dot, stripe, wave, cross and diamond markings (off by default; use Patterns to enable), stone pockets, permanent partitions, key-operated gates, varied cup capacities, concealed cups and level-specific slot limits. Cups show fill percentages; collecting every grain ends the level immediately.
• Undo restores the exact previous choice; Extra Slot is limited to one per attempt; Reveal uncovers the colors of one waiting cup.
• Mouse, touch, keyboard, pause, sound, fullscreen and local progress. No level timer.

Leave space for the next exposed color. A large cup can remain partly full while another color blocks its remaining sand. A smaller cup may clear sooner, but its lane also determines which cup becomes selectable next.

Sending several cups is useful when their colors can both reach the bottom. If all slots are taken, watch the streams before using a tool: a matching cup can collect a waiting pile on its next pass. Removing a cup opens a tile; newly exposed neighbors connected to the top opening reveal immediately. A revealed inner cup remains blocked until it has an open route. A closed gate needs its marked key cup first; Reveal cannot unlock it.

The first two levels introduce the loop. From level three, longer fixed queues and three slots demand more choices. Inner cups remain unknown until exposed, with different arrangements across the levels; nine is a two-slot challenge. Stone pockets begin at level three, star gates at six, and independent star and heart gates at fourteen. Plan which pocket to open while leaving belt space for the next sand color. Levels 21–30 develop this choice across two teaching pictures, five exploration pictures and three combined challenges; each has verified star-first and heart-first routes.

How do the sand and cups work?

The tray starts full of sand. Every grain obeys gravity and local support from the first frame. As lower grains leave through a gate, unsupported grains above collapse regardless of color, collide, pile up and mix. Floor gates open only when a matching cup will pass beneath the falling sand. Every delivered grain uses one unit of capacity.

Does a full conveyor mean I have lost?

No. A full loop keeps running while any cup can collect sand and finish. OUT OF SLOTS appears only when every slot is occupied and no remaining sand can make progress.

Why is a cup showing a question mark?

It has no open route to the top. Side and bottom walls also block access, even on a boundary. Remove reachable cups to open a route to it. Reveal can show one inner color, but does not let a surrounded cup move. Stone pegs, dividers and closed gates also block its route. Send the matching key cup to open an ordinary gate. A cup-seal gate stays closed until its marked cup reaches 100%. Its true color and capacity are fixed.

What does Undo restore?

Undo returns to the moment before your last cup choice, including the formation, gate state, sand positions, falling streams and cup fills. Your one extra slot and colors peeked with Reveal stay available, and the Undo charge stays spent.

Are tools, coins or advertisements required?

No payment or advertisement is required. Extra Slot adds at most one conveyor position per attempt and resets when you change or replay a level. Undo and Reveal have free local practice refills. Coins are earned once per first clear. No rewarded advertising service is connected.

Is Sand Loop timed, and is my progress saved?

There is no timer. Pause or leave the tab to stop the simulation. Completed levels, unlocked levels, coins, sound and tool supplies are saved in this browser. Reloading starts a fresh attempt at your selected unlocked level.