Solution to Endless Practice

Solvers are given starting values for A-J as well as 10 mini puzzles (see individual walkthroughs below). Entering the correct answer to each mini-puzzle unlocks an image of a mathematical iteration that assigns value to one variable. Each mini-puzzle also produces an extra letter.

In the order the puzzles are initially listed, these extra letters spell out ORDER BY CAR. The face/number image, the puzzle title, and the flavor text all hint toward the cartoon Infinity Train; specifically, the show's first season, which is called The Perennial Child. Each episode of that season is entitled “The (Something) Car” (except the 10th episode, “The Engine.”) The 10 mini puzzles represent the 10 episodes in the show's first season (e.g., Sunblock has solvers name famous beaches, and “The Beach Car” is one of the episodes). As a solving aid, the puzzles are initially listed in alphabetical order by the episode titles they represent.

Start each variable from A to J with its value in the initial image, under the faces (the specific faces are arbitrary; they’re just meant to clue Infinity Train).

Using the mathematical assignment statements associated with each puzzle in episode order, one at a time, assign new values to A-J, which are then used in subsequent operations.

Expression	Notes	New Value	A1Z26
	(G-B) = (101-100) = 1, and the logarithm of 1 is always 0.	0	(space)
	0!=1, so 3!+0!=7	7	G
	F=0; anything to the 0 power = 1	1	A
	If you plug the new values of H and D into this expression, it becomes 2, 4, 8, 16... So the sequence is “powers of 2”. The units digit rotates through 2, 4, 8, 6 over and over. The 115th term in that sequence will have a units digit of 8.	8	H
	This is the definition of the derivative of x^2 evaluated at 6. This means you plug 6 into 2x to get 12.	12	L
	This is a rational equation, with the same degree on the top and the bottom. Therefore, it has a horizontal asymptote equal to DCG/A, which is 14.	14	N
	I+AB is a multiple of 9. If you continuously add the digits of a multiple of 9 together, you will eventually get to 9.	9	I
	This is defining an integral using an infinite Riemann sum. This is equivalent to the integral from 6 to 8 of xdx, which is 14.	14	N
	D-H is 6, I is 9. Set the fraction equal to X. Replace the whole denominator of the fraction with X, to get X = 6-9/X. X solves to 3.	3	C
	This is an infinite geometric series. The initial term is 3, and the ratio is 4/5. Plugging this into the equation for the sum of an infinite geometric series, you get 15.	15	O

After all operations are performed, the new values of A-J in alphabetical order are alphanumeric for LONG CHAIN, the puzzle answer (the value of E becomes 0, indicating a space).

Mini-puzzle solutions are as follows:

Playplace (The Ball Pit Car)

The enumerations correspond to phrases (listed in alphabetical order, A-I) containing the word BALL, which can be found in the ball pit by combining the bigrams or trigrams in adjacent balls. In each phrase, the word BALL has been replaced by a new letter.

Reading the substituted letters in this order spells DROPS THE O, which becomes the puzzle answer DROPS THE BALL and a leftover O

Sunblock (The Beach Car)

First, identify the images pictured. Then, per the flavor text, take the SPF rating from each bottle and “block out” the first SPF% of each item's name. For example, blocking off the first 80% of BATTLESHIP yields IP, and blocking out the first 33% of SINEMA yields NEMA.

The resulting strings can be combined to form the names of famous beaches, minus one letter. The locations of these beaches are the locations given at the bottom of the puzzle page.

Match up the beach names and read the missing letters in order to get the puzzle answer BAHAMIAN.

In addition, every bottle has a Morse code R as a design element, yielding an extra R.

Mouse Taken (The Cat's Car)

“Mouse Taken” is an anagram of “Neko Atsume,” a game about collecting vicious predators. This is a puzzle about cats! Each image clues the name of one of the game’s collectible Regular Cats.

Each row or column of the grid also features an orange, white, gray, or black stripe. In each row of the grid, the colorations for two of the cats exactly match the stripe colors for their respective row and column. Indexing the leftmost matching cat in each row with the number to the left of the row and the rightmost cat with the number to the right of the row gives the answer going down the columns: HELLO KITTY.

The correctly colored cats compose the critical character: D

To-Do (The Chrome Car)

Each icon in the browser’s open tabs belongs to a famous website. Each site can be matched up with one of the items in the to-do list such that it points to a different popular website that has similar properties (there may be many such websites but one is always significantly more popular – sorry, Yahoo! Mail fans). Those websites, in turn, have icons that prominently feature letters – some one letter, some two. Ordering those icons as their rivals are ordered in the browser tabs spells out the answer, WINDOW PANE:

The final line says to find a new browser from a massive tech company. The current browser is Chrome, as the icon in the top left shows. Its biggest rival that both matches the description and has a letter for its icon is Edge (formerly Explorer – “either old or new should work” because they lead to the same letter). That letter, the extracted letter for this puzzle, is E.

Castle Crisis (The Corgi Car)

The word search contains the word CORGI like a million times. Find every instance of CORGI, and the unused letters spell out the caterer’s name (and the answer to the puzzle), GIORGIO’S ROCOCO GNOCCHI, plus RRRRR, to indicate the leftover R.

The Cracked Crystal (The Crystal Car)

Every line connects two words that form a two-word or compound phrase. Fill in these words. The arrows on the connecting line indicate which word comes first.

Certain word boxes connect to spaces in the corner boxes. Index into those words using the number below its corresponding space to get SILLY and CHASE on the top, and FIST and HEADS on the bottom. Do one more connection to get the puzzle answer GOOSEBUMP

The clues numbered 1-10 point toward specific two-word combinations in the diagram. Each clue contains either the word “First” or “After” to indicate whether to use the first or second word in the two-word combinations. Connecting these words gives the shape of the letter B.

CLEAN BREAK→CONTROL TOWER→CONTROL PANEL→DRUM BEAT→PLAY STATION→WATER TOWER→DRY ICE→STONE AGE→PARKING TICKET→PAGE BREAK

The Pitch (The Engine)

The writer’s pitch contains 10 “car crashes,” which, in classic cryptic crossword style, refer to 10 anagrams of car makes. (As the movie is “a period piece,” all 10 are brands that are discontinued in the US). A red dot appears in the upper right corner of the screen every time one of the anagrams is spoken.

At the end of the pitch, the producer lists a string of numbers. Use those numbers to index into the unscrambled car makes to get the answer, A LARGE ROOM.

The Producer’s Name, Y. Y. Wise, clues the leftover letter for this puzzle, Y.

Off the Grid (The Grid Car)

Solve the Cryptic crossword:

Six of the answers contain the letter string GRID: GRIDLOCK, HAGRID, SMART GRID, GRIDDLE, INGRID and LOG RIDE.

When entered in the crossword grid, the GRID is dropped and replaced by a letter from the crossing word, resulting in (F)LOCK, HA(L), SMART(Y), (I)DLE, IN(N), and LO(G)E. The replacement letters, read left to right, spell FLYING, the puzzle’s answer.

In addition, two of the puzzle’s clues describe the letter C as “a letter of particular importance,” as it is the leftover letter for this puzzle.

Historical Pictures (The Past Car)

Each of the images is taken from a previous Mystery Hunt, one from each year from 2012 to 2020. Order the images by year, and use the number of the image to index into the name of the round that the image is from, to get the answer CHAMELEON.

“The most important one was the chess one”... that would be the image from 2014, which gave us the A, which is our extra letter.

Unfinished Symphonies (The Unfinished Car)

It’s a standard crossword. However, eight of the clue entries are unfinished song titles by the artists listed in the flavortext. In flavortext order:

The missing letters spell puzzle answer MOTOR VEHICLE.

In addition, there are several colored squares in the grid. The squares are (more or less) in the shape of an R, and when the grid is filled, they all contain an R, so R is your leftover letter.