DOWNSTACKING & DEFENCE · LESSON 1 OF 3
Reading garbage
AFTER THIS GUIDEYou can follow the hole column through several garbage rows and identify which one is reachable now.
The target is a route through the rows.
Ordinary garbage rows arrive with missing cells. When several holes align, one vertical channel can clear several rows efficiently. When the holes change column frequently, you need more changes of direction. Players often call these broad shapes clean garbage and cheese.
Read from the highest accessible garbage row downwards. Its hole is your immediate target. Then look at the hole below the first group: that is where the next route must lead after your clear.
The bottom-most hole may be the eventual destination, but placing towards it too early can bury the current entrance. A downstack plan needs an order of access, not merely an arrow pointing at the floor.
Distinguish the grey garbage from blocks you have added. Clearing a high row of your own blocks may be necessary to expose garbage, but repeatedly rebuilding above the hole can make the dig slower. Ask which placement gets you closer to the next grey row.
Trace an aligned channel, then a changing one
Read clean garbage
In the clean example, follow the continuous empty column. A piece can travel down it from above. Count how many rows share the route.
Read cheese
In the messy example, follow the missing cell in each row. Find the first change of column. That change tells you where residue from your first clear could become an obstruction.
Check the leftover cell
Step through the downstack animation. I removes three garbage rows, but one of its cells remains. The clear helps, yet the board is not empty. Include that cell in the next plan.
These four garbage rows share one gap column. An I can clear all four once the entry is open.
Clearing the top gap is only the first step. Read the next gap before placing blocks that will survive the clear.
The channel is open from above.
A vertical I completes three garbage rows.
The garbage is gone. One cell remains, so this is not a Perfect Clear.
Common mistakes
Chasing the lowest visible hole first
Reach it by clearing the rows above in a usable order. The visually deepest target may be inaccessible now.
Calling every line clear progress
A clear can remove a restriction, but adding several new layers for it may be costly. Track whether you are exposing garbage or merely moving your own blocks around.
Ignoring residue
One leftover block can sit directly above the next hole. Read the after-clear board before committing to the next piece.
TAKE IT TO THE BOARD
Predict the next hole five times
- Open Downstacking with Gravity Off and NEXT 5. Choose the slowest garbage interval while learning; automatic falling and incoming garbage are separate controls.
- Before each of five clears, name the current target column and the next hole that should become reachable.
- After each clear, compare the result. Pause the session to study if incoming rows make the board difficult to read.
What counts as progress? Your prediction of the next accessible hole matches the board after the clear.
Open practice ↗Opens the mode. Set Gravity and NEXT yourself; your current settings are kept.
Keep these terms nearby
NEXT IN THIS PATH
Finding the route
Plan the order of clears and keep the next hole reachable.
Read the next guide →Further reading
For setup variations and additional examples, see How to Tetris: Downstacking. The practice task here is original to Stacking Lab.