Daily Shikaku
The rule
Cut the whole grid into rectangles. Each one holds exactly one number, and that number is how many squares it covers.
Drag from one corner of a block to the other to draw it. Tap a block you have drawn to take it off again. A block that does not match its number shows red.
Where to start
Look for numbers with few ways to sit. A 5 or a 7 is prime, so its block is a single line of that length, and near an edge there may be only one place it can go. Then work out from there: every square has to end up inside something, so a square only one number can reach belongs to that number.
In your hands
Packing a tray with pieces is the same instinct in three dimensions. See the packing puzzles.
Solvable Without Guessing
Every grid here was generated and then handed to a solver that is only allowed techniques a person can use. If it could not finish without a guess, the puzzle was thrown away rather than published. That also makes the answer unique, which is why the page can check your work by the rules alone rather than against a stored answer.
More to Play
There are twenty one daily sudoku variants, a hitori, tents, a minesweeper with the guessing removed and a tower of hanoi. For puzzles you can hold, see mechanical puzzles.