# T-Rex Runner - credits and notes

**The game.** The Dinosaur Game (the "Chrome Dino", "T-Rex Runner") is the endless runner built into
Google Chrome's offline error page. It was made in 2014 by Sebastien Gabriel, Alan Bettes and Edward
Jung of the Chrome UX team (codename "Project Bolan"; the character is the "Lonely T-Rex"), released in
September 2014, given pterodactyls in 2015 and a saved high score in 2018. Its source code lives in the
Chromium project under a BSD-3 licence (components/neterror/resources/dino_game/).

**This recreation** (https://t-rex-runner.skillsafe.ai/) ports the game's MECHANICS AND CONSTANTS from
that source, exactly: the 600 x 150 stage, 60 Hz time-based stepping, start speed 6 rising by 0.001 per
tick to 13, the jump (velocity -10 minus speed/10, gravity 0.6, the 30-pixel minimum jump, the drop
velocity -5 on release, the x3 speed drop on Down), the duck, the intro that opens the canvas on the
first landing, 3 seconds before the first obstacle, small cacti (17 x 35, groups above speed 4), large
cacti (25 x 50, groups above speed 7), pterodactyls (46 x 40, at three heights, only above speed 8.5, at
+-0.8 the ground speed, two frames at 1000/6 ms), the gap formula width*speed + minGap*0.6 with a x1.5
maximum, the two-in-a-row duplication limit, the per-part collision boxes, the score (0.025 points per
pixel, five digits growing to six), the flashing achievement every 100 points, night mode every 700
points for 12 seconds with the seven moon phases and two stars, clouds (46 x 14, 0.2 x speed, at most
six), the flat and bumpy ground segments, the game-over text and the restart button that draws itself
in, restart on Enter or a tap at once and on Space after 1.2 seconds, the blinking idle T-Rex (three
blinks), pause on blur, the high score with tap-twice-to-reset, the slow "accessibility" speed mode
(4.2 to 9) and gamepad buttons 0/1/9.

**What is ours.** Every pixel of art (the T-Rex, cacti, pterodactyl, cloud, moon, stars, digits, the
GAME OVER text, the restart button, the ground) is drawn in our own code and shares only the frame
DIMENSIONS with the original so the ported collision boxes stay valid. The three sounds are synthesised
tones of our own design. The page text, the help and this code are ours (MIT licence, see LICENSE.txt).

**Additions, labelled on the page:** a seed number in the link (#617) that replays the same obstacle
course; a sound toggle; a dark-theme toggle; an "Arcade mode" button (the original scales like this at
chrome://dino); a hold-to-duck button on touch screens (the original has no touch duck; its pterodactyls
fly only at two heights on phones, which we keep); a statistics dialog; the high score kept in this
browser's storage (Chrome keeps it in the profile); a paused game surviving a reload.

**Not ported:** the birthday-cake and Olympic-torch Easter eggs ("alt game modes"), the screen-reader
audio-cue mode with generated footsteps, and phone vibration.

Not affiliated with or endorsed by Google. Chrome and Chromium are trademarks of Google LLC.

References: the Chromium source (chromium.googlesource.com, components/neterror/resources/dino_game/,
BSD-3) for every constant and rule; Wikipedia, "Dinosaur Game", for the history.

The Chromium BSD-3 licence and copyright notice (The Chromium Authors) that covers the ported
mechanics, constants and collision boxes is reproduced in full in LICENSE-CHROMIUM.txt.