code.delx.au - gnu-emacs/blob - lisp/play/tetris.el

   1 ;;; tetris.el --- implementation of Tetris for Emacs
   2
   3 ;; Copyright (C) 1997, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
   4 ;;   2009, 2010, 2011  Free Software Foundation, Inc.
   5
   6 ;; Author: Glynn Clements <glynn@sensei.co.uk>
   7 ;; Version: 2.01
   8 ;; Created: 1997-08-13
   9 ;; Keywords: games
  10
  11 ;; This file is part of GNU Emacs.
  12
  13 ;; GNU Emacs is free software: you can redistribute it and/or modify
  14 ;; it under the terms of the GNU General Public License as published by
  15 ;; the Free Software Foundation, either version 3 of the License, or
  16 ;; (at your option) any later version.
  17
  18 ;; GNU Emacs is distributed in the hope that it will be useful,
  19 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  21 ;; GNU General Public License for more details.
  22
  23 ;; You should have received a copy of the GNU General Public License
  24 ;; along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.
  25
  26 ;;; Commentary:
  27
  28 ;;; Code:
  29
  30 (eval-when-compile
  31   (require 'cl))
  32
  33 (require 'gamegrid)
  34
  35 ;; ;;;;;;;;;;;;; customization variables ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
  36
  37 (defgroup tetris nil
  38   "Play a game of Tetris."
  39   :prefix "tetris-"
  40   :group 'games)
  41
  42 (defcustom tetris-use-glyphs t
  43   "Non-nil means use glyphs when available."
  44   :group 'tetris
  45   :type 'boolean)
  46
  47 (defcustom tetris-use-color t
  48   "Non-nil means use color when available."
  49   :group 'tetris
  50   :type 'boolean)
  51
  52 (defcustom tetris-draw-border-with-glyphs t
  53   "Non-nil means draw a border even when using glyphs."
  54   :group 'tetris
  55   :type 'boolean)
  56
  57 (defcustom tetris-default-tick-period 0.3
  58   "The default time taken for a shape to drop one row."
  59   :group 'tetris
  60   :type 'number)
  61
  62 (defcustom tetris-update-speed-function
  63   'tetris-default-update-speed-function
  64   "Function run whenever the Tetris score changes.
  65 Called with two arguments: (SHAPES ROWS)
  66 SHAPES is the number of shapes which have been dropped.
  67 ROWS is the number of rows which have been completed.
  68
  69 If the return value is a number, it is used as the timer period."
  70   :group 'tetris
  71   :type 'function)
  72
  73 (defcustom tetris-mode-hook nil
  74   "Hook run upon starting Tetris."
  75   :group 'tetris
  76   :type 'hook)
  77
  78 (defcustom tetris-tty-colors
  79   ["blue" "white" "yellow" "magenta" "cyan" "green" "red"]
  80   "Vector of colors of the various shapes in text mode."
  81   :group 'tetris
  82   :type (let ((names `("Shape 1" "Shape 2" "Shape 3"
  83                        "Shape 4" "Shape 5" "Shape 6" "Shape 7"))
  84               (result nil))
  85           (while names
  86             (add-to-list 'result
  87                          (cons 'choice
  88                                (cons :tag
  89                                      (cons (car names)
  90                                            (mapcar (lambda (color)
  91                                                      (list 'const color))
  92                                                    (defined-colors)))))
  93                          t)
  94             (setq names (cdr names)))
  95           result))
  96
  97 (defcustom tetris-x-colors
  98   [[0 0 1] [0.7 0 1] [1 1 0] [1 0 1] [0 1 1] [0 1 0] [1 0 0]]
  99   "Vector of colors of the various shapes."
 100   :group 'tetris
 101   :type 'sexp)
 102
 103 (defcustom tetris-buffer-name "*Tetris*"
 104   "Name used for Tetris buffer."
 105   :group 'tetris
 106   :type 'string)
 107
 108 (defcustom tetris-buffer-width 30
 109   "Width of used portion of buffer."
 110   :group 'tetris
 111   :type 'number)
 112
 113 (defcustom tetris-buffer-height 22
 114   "Height of used portion of buffer."
 115   :group 'tetris
 116   :type 'number)
 117
 118 (defcustom tetris-width 10
 119   "Width of playing area."
 120   :group 'tetris
 121   :type 'number)
 122
 123 (defcustom tetris-height 20
 124   "Height of playing area."
 125   :group 'tetris
 126   :type 'number)
 127
 128 (defcustom tetris-top-left-x 3
 129   "X position of top left of playing area."
 130   :group 'tetris
 131   :type 'number)
 132
 133 (defcustom tetris-top-left-y 1
 134   "Y position of top left of playing area."
 135   :group 'tetris
 136   :type 'number)
 137
 138 (defvar tetris-next-x (+ (* 2 tetris-top-left-x) tetris-width)
 139   "X position of next shape.")
 140
 141 (defvar tetris-next-y tetris-top-left-y
 142   "Y position of next shape.")
 143
 144 (defvar tetris-score-x tetris-next-x
 145   "X position of score.")
 146
 147 (defvar tetris-score-y (+ tetris-next-y 6)
 148   "Y position of score.")
 149
 150 ;; It is not safe to put this in /tmp.
 151 ;; Someone could make a symlink in /tmp
 152 ;; pointing to a file you don't want to clobber.
 153 (defvar tetris-score-file "tetris-scores"
 154 ;; anybody with a well-connected server want to host this?
 155 ;(defvar tetris-score-file "/anonymous@ftp.pgt.com:/pub/cgw/tetris-scores"
 156   "File for holding high scores.")
 157
 158 ;; ;;;;;;;;;;;;; display options ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 159
 160 (defvar tetris-blank-options
 161   '(((glyph colorize)
 162      (t ?\040))
 163     ((color-x color-x)
 164      (mono-x grid-x)
 165      (color-tty color-tty))
 166     (((glyph color-x) [0 0 0])
 167      (color-tty "black"))))
 168
 169 (defvar tetris-cell-options
 170   '(((glyph colorize)
 171      (emacs-tty ?O)
 172      (t ?\040))
 173     ((color-x color-x)
 174      (mono-x mono-x)
 175      (color-tty color-tty)
 176      (mono-tty mono-tty))
 177     ;; color information is taken from tetris-x-colors and tetris-tty-colors
 178     ))
 179
 180 (defvar tetris-border-options
 181   '(((glyph colorize)
 182      (t ?\+))
 183     ((color-x color-x)
 184      (mono-x grid-x)
 185      (color-tty color-tty))
 186     (((glyph color-x) [0.5 0.5 0.5])
 187      (color-tty "white"))))
 188
 189 (defvar tetris-space-options
 190   '(((t ?\040))
 191     nil
 192     nil))
 193
 194 ;; ;;;;;;;;;;;;; constants ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 195
 196 (defconst tetris-shapes
 197   [[[[0  0] [1  0] [0  1] [1  1]]]
 198
 199    [[[0  0] [1  0] [2  0] [2  1]]
 200     [[1 -1] [1  0] [1  1] [0  1]]
 201     [[0 -1] [0  0] [1  0] [2  0]]
 202     [[1 -1] [2 -1] [1  0] [1  1]]]
 203
 204    [[[0  0] [1  0] [2  0] [0  1]]
 205     [[0 -1] [1 -1] [1  0] [1  1]]
 206     [[2 -1] [0  0] [1  0] [2  0]]
 207     [[1 -1] [1  0] [1  1] [2  1]]]
 208
 209    [[[0  0] [1  0] [1  1] [2  1]]
 210     [[1  0] [0  1] [1  1] [0  2]]]
 211
 212    [[[1  0] [2  0] [0  1] [1  1]]
 213     [[0  0] [0  1] [1  1] [1  2]]]
 214
 215    [[[1  0] [0  1] [1  1] [2  1]]
 216     [[1  0] [1  1] [2  1] [1  2]]
 217     [[0  1] [1  1] [2  1] [1  2]]
 218     [[1  0] [0  1] [1  1] [1  2]]]
 219
 220    [[[0  0] [1  0] [2  0] [3  0]]
 221     [[1 -1] [1  0] [1  1] [1  2]]]]
 222   "Each shape is described by a vector that contains the coordinates of
 223 each one of its four blocks.")
 224
 225 ;;the scoring rules were taken from "xtetris".  Blocks score differently
 226 ;;depending on their rotation
 227
 228 (defconst tetris-shape-scores
 229   [[6] [6 7 6 7] [6 7 6 7] [6 7] [6 7] [5 5 6 5] [5 8]] )
 230
 231 (defconst tetris-shape-dimensions
 232   [[2 2] [3 2] [3 2] [3 2] [3 2] [3 2] [4 1]])
 233
 234 (defconst tetris-blank 7)
 235
 236 (defconst tetris-border 8)
 237
 238 (defconst tetris-space 9)
 239
 240 (defun tetris-default-update-speed-function (shapes rows)
 241   (/ 20.0 (+ 50.0 rows)))
 242
 243 ;; ;;;;;;;;;;;;; variables ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 244
 245 (defvar tetris-shape 0)
 246 (defvar tetris-rot 0)
 247 (defvar tetris-next-shape 0)
 248 (defvar tetris-n-shapes 0)
 249 (defvar tetris-n-rows 0)
 250 (defvar tetris-score 0)
 251 (defvar tetris-pos-x 0)
 252 (defvar tetris-pos-y 0)
 253 (defvar tetris-paused nil)
 254
 255 (make-variable-buffer-local 'tetris-shape)
 256 (make-variable-buffer-local 'tetris-rot)
 257 (make-variable-buffer-local 'tetris-next-shape)
 258 (make-variable-buffer-local 'tetris-n-shapes)
 259 (make-variable-buffer-local 'tetris-n-rows)
 260 (make-variable-buffer-local 'tetris-score)
 261 (make-variable-buffer-local 'tetris-pos-x)
 262 (make-variable-buffer-local 'tetris-pos-y)
 263 (make-variable-buffer-local 'tetris-paused)
 264
 265 ;; ;;;;;;;;;;;;; keymaps ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 266
 267 (defvar tetris-mode-map
 268   (let ((map (make-sparse-keymap 'tetris-mode-map)))
 269     (define-key map "n"         'tetris-start-game)
 270     (define-key map "q"         'tetris-end-game)
 271     (define-key map "p"         'tetris-pause-game)
 272
 273     (define-key map " "         'tetris-move-bottom)
 274     (define-key map [left]      'tetris-move-left)
 275     (define-key map [right]     'tetris-move-right)
 276     (define-key map [up]        'tetris-rotate-prev)
 277     (define-key map [down]      'tetris-rotate-next)
 278     map))
 279
 280 (defvar tetris-null-map
 281   (let ((map (make-sparse-keymap 'tetris-null-map)))
 282     (define-key map "n"         'tetris-start-game)
 283     map))
 284
 285 ;; ;;;;;;;;;;;;;;;; game functions ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 286
 287 (defun tetris-display-options ()
 288   (let ((options (make-vector 256 nil)))
 289     (loop for c from 0 to 255 do
 290       (aset options c
 291             (cond ((= c tetris-blank)
 292                     tetris-blank-options)
 293                   ((and (>= c 0) (<= c 6))
 294                    (append
 295                     tetris-cell-options
 296                     `((((glyph color-x) ,(aref tetris-x-colors c))
 297                        (color-tty ,(aref tetris-tty-colors c))
 298                        (t nil)))))
 299                    ((= c tetris-border)
 300                     tetris-border-options)
 301                    ((= c tetris-space)
 302                     tetris-space-options)
 303                   (t
 304                    '(nil nil nil)))))
 305     options))
 306
 307 (defun tetris-get-tick-period ()
 308   (if (boundp 'tetris-update-speed-function)
 309       (let ((period (apply tetris-update-speed-function
 310                            tetris-n-shapes
 311                            tetris-n-rows nil)))
 312         (and (numberp period) period))))
 313
 314 (defun tetris-get-shape-cell (block)
 315   (aref (aref  (aref tetris-shapes
 316                      tetris-shape) tetris-rot)
 317         block))
 318
 319 (defun tetris-shape-width ()
 320   (aref (aref tetris-shape-dimensions tetris-shape) 0))
 321
 322 (defun tetris-shape-rotations ()
 323   (length (aref tetris-shapes tetris-shape)))
 324
 325 (defun tetris-draw-score ()
 326   (let ((strings (vector (format "Shapes: %05d" tetris-n-shapes)
 327                          (format "Rows:   %05d" tetris-n-rows)
 328                          (format "Score:  %05d" tetris-score))))
 329     (loop for y from 0 to 2 do
 330           (let* ((string (aref strings y))
 331                  (len (length string)))
 332             (loop for x from 0 to (1- len) do
 333                   (gamegrid-set-cell (+ tetris-score-x x)
 334                                      (+ tetris-score-y y)
 335                                      (aref string x)))))))
 336
 337 (defun tetris-update-score ()
 338   (tetris-draw-score)
 339   (let ((period (tetris-get-tick-period)))
 340     (if period (gamegrid-set-timer period))))
 341
 342 (defun tetris-new-shape ()
 343   (setq tetris-shape tetris-next-shape)
 344   (setq tetris-rot 0)
 345   (setq tetris-next-shape (random 7))
 346   (setq tetris-pos-x (/ (- tetris-width (tetris-shape-width)) 2))
 347   (setq tetris-pos-y 0)
 348   (if (tetris-test-shape)
 349       (tetris-end-game)
 350     (tetris-draw-shape)
 351     (tetris-draw-next-shape)
 352     (tetris-update-score)))
 353
 354 (defun tetris-draw-next-shape ()
 355   (loop for x from 0 to 3 do
 356         (loop for y from 0 to 3 do
 357               (gamegrid-set-cell (+ tetris-next-x x)
 358                                  (+ tetris-next-y y)
 359                                  tetris-blank)))
 360   (loop for i from 0 to 3 do
 361         (let ((tetris-shape tetris-next-shape)
 362               (tetris-rot 0))
 363           (gamegrid-set-cell (+ tetris-next-x
 364                                 (aref (tetris-get-shape-cell i) 0))
 365                              (+ tetris-next-y
 366                                 (aref (tetris-get-shape-cell i) 1))
 367                              tetris-shape))))
 368
 369 (defun tetris-draw-shape ()
 370   (loop for i from 0 to 3 do
 371         (let ((c (tetris-get-shape-cell i)))
 372           (gamegrid-set-cell (+ tetris-top-left-x
 373                                 tetris-pos-x
 374                                 (aref c 0))
 375                              (+ tetris-top-left-y
 376                                 tetris-pos-y
 377                                 (aref c 1))
 378                              tetris-shape))))
 379
 380 (defun tetris-erase-shape ()
 381   (loop for i from 0 to 3 do
 382         (let ((c (tetris-get-shape-cell i)))
 383           (gamegrid-set-cell (+ tetris-top-left-x
 384                                 tetris-pos-x
 385                                 (aref c 0))
 386                              (+ tetris-top-left-y
 387                                 tetris-pos-y
 388                                 (aref c 1))
 389                              tetris-blank))))
 390
 391 (defun tetris-test-shape ()
 392   (let ((hit nil))
 393     (loop for i from 0 to 3 do
 394           (unless hit
 395             (setq hit
 396                   (let* ((c (tetris-get-shape-cell i))
 397                          (xx (+ tetris-pos-x
 398                                 (aref c 0)))
 399                          (yy (+ tetris-pos-y
 400                                 (aref c 1))))
 401                     (or (>= xx tetris-width)
 402                         (>= yy tetris-height)
 403                         (/= (gamegrid-get-cell
 404                              (+ xx tetris-top-left-x)
 405                              (+ yy tetris-top-left-y))
 406                             tetris-blank))))))
 407     hit))
 408
 409 (defun tetris-full-row (y)
 410   (let ((full t))
 411     (loop for x from 0 to (1- tetris-width) do
 412           (if (= (gamegrid-get-cell (+ tetris-top-left-x x)
 413                                     (+ tetris-top-left-y y))
 414                  tetris-blank)
 415               (setq full nil)))
 416     full))
 417
 418 (defun tetris-shift-row (y)
 419   (if (= y 0)
 420       (loop for x from 0 to (1- tetris-width) do
 421         (gamegrid-set-cell (+ tetris-top-left-x x)
 422                            (+ tetris-top-left-y y)
 423                            tetris-blank))
 424   (loop for x from 0 to (1- tetris-width) do
 425         (let ((c (gamegrid-get-cell (+ tetris-top-left-x x)
 426                                     (+ tetris-top-left-y y -1))))
 427           (gamegrid-set-cell (+ tetris-top-left-x x)
 428                              (+ tetris-top-left-y y)
 429                            c)))))
 430
 431 (defun tetris-shift-down ()
 432   (loop for y0 from 0 to (1- tetris-height) do
 433         (if (tetris-full-row y0)
 434             (progn (setq tetris-n-rows (1+ tetris-n-rows))
 435                    (loop for y from y0 downto 0 do
 436                          (tetris-shift-row y))))))
 437
 438 (defun tetris-draw-border-p ()
 439   (or (not (eq gamegrid-display-mode 'glyph))
 440       tetris-draw-border-with-glyphs))
 441
 442 (defun tetris-init-buffer ()
 443   (gamegrid-init-buffer tetris-buffer-width
 444                         tetris-buffer-height
 445                         tetris-space)
 446   (let ((buffer-read-only nil))
 447     (if (tetris-draw-border-p)
 448         (loop for y from -1 to tetris-height do
 449               (loop for x from -1 to tetris-width do
 450                     (gamegrid-set-cell (+ tetris-top-left-x x)
 451                                        (+ tetris-top-left-y y)
 452                                        tetris-border))))
 453     (loop for y from 0 to (1- tetris-height) do
 454           (loop for x from 0 to (1- tetris-width) do
 455                 (gamegrid-set-cell (+ tetris-top-left-x x)
 456                                    (+ tetris-top-left-y y)
 457                                    tetris-blank)))
 458     (if (tetris-draw-border-p)
 459         (loop for y from -1 to 4 do
 460               (loop for x from -1 to 4 do
 461                     (gamegrid-set-cell (+ tetris-next-x x)
 462                                        (+ tetris-next-y y)
 463                                        tetris-border))))))
 464
 465 (defun tetris-reset-game ()
 466   (gamegrid-kill-timer)
 467   (tetris-init-buffer)
 468   (setq tetris-next-shape (random 7))
 469   (setq tetris-shape    0
 470         tetris-rot      0
 471         tetris-pos-x    0
 472         tetris-pos-y    0
 473         tetris-n-shapes 0
 474         tetris-n-rows   0
 475         tetris-score    0
 476         tetris-paused   nil)
 477   (tetris-new-shape))
 478
 479 (defun tetris-shape-done ()
 480   (tetris-shift-down)
 481   (setq tetris-n-shapes (1+ tetris-n-shapes))
 482   (setq tetris-score
 483         (+ tetris-score
 484            (aref (aref tetris-shape-scores tetris-shape) tetris-rot)))
 485   (tetris-update-score)
 486   (tetris-new-shape))
 487
 488 (defun tetris-update-game (tetris-buffer)
 489   "Called on each clock tick.
 490 Drops the shape one square, testing for collision."
 491   (if (and (not tetris-paused)
 492            (eq (current-buffer) tetris-buffer))
 493       (let (hit)
 494         (tetris-erase-shape)
 495         (setq tetris-pos-y (1+ tetris-pos-y))
 496         (setq hit (tetris-test-shape))
 497         (if hit
 498             (setq tetris-pos-y (1- tetris-pos-y)))
 499         (tetris-draw-shape)
 500         (if hit
 501             (tetris-shape-done)))))
 502
 503 (defun tetris-move-bottom ()
 504   "Drop the shape to the bottom of the playing area."
 505   (interactive)
 506   (unless tetris-paused
 507     (let ((hit nil))
 508       (tetris-erase-shape)
 509       (while (not hit)
 510         (setq tetris-pos-y (1+ tetris-pos-y))
 511         (setq hit (tetris-test-shape)))
 512       (setq tetris-pos-y (1- tetris-pos-y))
 513       (tetris-draw-shape)
 514       (tetris-shape-done))))
 515
 516 (defun tetris-move-left ()
 517   "Move the shape one square to the left."
 518   (interactive)
 519   (unless tetris-paused
 520     (tetris-erase-shape)
 521     (setq tetris-pos-x (1- tetris-pos-x))
 522     (if (tetris-test-shape)
 523         (setq tetris-pos-x (1+ tetris-pos-x)))
 524     (tetris-draw-shape)))
 525
 526 (defun tetris-move-right ()
 527   "Move the shape one square to the right."
 528   (interactive)
 529   (unless tetris-paused
 530     (tetris-erase-shape)
 531     (setq tetris-pos-x (1+ tetris-pos-x))
 532     (if (tetris-test-shape)
 533         (setq tetris-pos-x (1- tetris-pos-x)))
 534     (tetris-draw-shape)))
 535
 536 (defun tetris-rotate-prev ()
 537   "Rotate the shape clockwise."
 538   (interactive)
 539   (unless tetris-paused
 540       (tetris-erase-shape)
 541       (setq tetris-rot (% (+ 1 tetris-rot)
 542                           (tetris-shape-rotations)))
 543       (if (tetris-test-shape)
 544           (setq tetris-rot (% (+ 3 tetris-rot)
 545                               (tetris-shape-rotations))))
 546       (tetris-draw-shape)))
 547
 548 (defun tetris-rotate-next ()
 549   "Rotate the shape anticlockwise."
 550   (interactive)
 551   (unless tetris-paused
 552         (tetris-erase-shape)
 553         (setq tetris-rot (% (+ 3 tetris-rot)
 554                             (tetris-shape-rotations)))
 555         (if (tetris-test-shape)
 556             (setq tetris-rot (% (+ 1 tetris-rot)
 557                                 (tetris-shape-rotations))))
 558         (tetris-draw-shape)))
 559
 560 (defun tetris-end-game ()
 561   "Terminate the current game."
 562   (interactive)
 563   (gamegrid-kill-timer)
 564   (use-local-map tetris-null-map)
 565   (gamegrid-add-score tetris-score-file tetris-score))
 566
 567 (defun tetris-start-game ()
 568   "Start a new game of Tetris."
 569   (interactive)
 570   (tetris-reset-game)
 571   (use-local-map tetris-mode-map)
 572   (let ((period (or (tetris-get-tick-period)
 573                     tetris-default-tick-period)))
 574     (gamegrid-start-timer period 'tetris-update-game)))
 575
 576 (defun tetris-pause-game ()
 577   "Pause (or resume) the current game."
 578   (interactive)
 579   (setq tetris-paused (not tetris-paused))
 580   (message (and tetris-paused "Game paused (press p to resume)")))
 581
 582 (defun tetris-active-p ()
 583   (eq (current-local-map) tetris-mode-map))
 584
 585 (put 'tetris-mode 'mode-class 'special)
 586
 587 (define-derived-mode tetris-mode nil "Tetris"
 588   "A mode for playing Tetris."
 589
 590   (add-hook 'kill-buffer-hook 'gamegrid-kill-timer nil t)
 591
 592   (use-local-map tetris-null-map)
 593
 594   (unless (featurep 'emacs)
 595     (setq mode-popup-menu
 596           '("Tetris Commands"
 597             ["Start new game"   tetris-start-game]
 598             ["End game"         tetris-end-game
 599              (tetris-active-p)]
 600             ["Pause"            tetris-pause-game
 601              (and (tetris-active-p) (not tetris-paused))]
 602             ["Resume"           tetris-pause-game
 603              (and (tetris-active-p) tetris-paused)])))
 604
 605   (setq show-trailing-whitespace nil)
 606
 607   (setq gamegrid-use-glyphs tetris-use-glyphs)
 608   (setq gamegrid-use-color tetris-use-color)
 609
 610   (gamegrid-init (tetris-display-options)))
 611
 612 ;;;###autoload
 613 (defun tetris ()
 614   "Play the Tetris game.
 615 Shapes drop from the top of the screen, and the user has to move and
 616 rotate the shape to fit in with those at the bottom of the screen so
 617 as to form complete rows.
 618
 619 tetris-mode keybindings:
 620    \\<tetris-mode-map>
 621 \\[tetris-start-game]   Starts a new game of Tetris
 622 \\[tetris-end-game]     Terminates the current game
 623 \\[tetris-pause-game]   Pauses (or resumes) the current game
 624 \\[tetris-move-left]    Moves the shape one square to the left
 625 \\[tetris-move-right]   Moves the shape one square to the right
 626 \\[tetris-rotate-prev]  Rotates the shape clockwise
 627 \\[tetris-rotate-next]  Rotates the shape anticlockwise
 628 \\[tetris-move-bottom]  Drops the shape to the bottom of the playing area
 629
 630 "
 631   (interactive)
 632
 633   (select-window (or (get-buffer-window tetris-buffer-name)
 634                      (selected-window)))
 635   (switch-to-buffer tetris-buffer-name)
 636   (gamegrid-kill-timer)
 637   (tetris-mode)
 638   (tetris-start-game))
 639
 640 (random t)
 641
 642 (provide 'tetris)
 643
 644 ;;; tetris.el ends here