DayTrippers Planet Generation System

Apr 17, 2025

The interstellar destination below was created using the DayTrippers Planet Generation rules (now in beta testing). Click here to generate another one.

0) {
$planetCount += rand(1,6);
$planetCountDice–;
}
return $planetCount;
}

function planetSize($planetMod) {
$planetSizeArray = array(“”, “”, “Small Rock Planet”, “Small Rock Planet”, “Asteroid”, “Moon”, “Artificial Satellite”, “Medium Rock Planet”, “Large Rock Planet”, “Gas Giant”, “Gas Giant”, “Gas Giant”, “Rogue Planet”);
$gravityModArray = array(0, 0, -3, -3, -3, -5, -2, -1, 0, 5, 5, 5, -3);
$planetSizeRoll = rand(1,6) + rand(1,6) + $planetMod;
if($planetSizeRoll < 2) { $planetSizeRoll = 2; } if($planetSizeRoll > 12) {
$planetSizeRoll = 12;
}
$planetSize = $planetSizeArray[$planetSizeRoll];
$gravityMod = $gravityModArray[$planetSizeRoll];
return array($planetSize, $gravityMod);
}

function gravity($gravityMod) {
$gravityBase = 0;
$divide = 0;
$gravityArray = array(“”, “”, “12”, “12”, “12”, “11”, “11”, “1”, “2”, “2”, “2”, “4”, “4”, “4”, “6”);
$atmoModArray = array(0, 0, -2, -2, -2, -1, -1, 0, 3, 3, 3, 5, 5, 5, 6);
$gravityRoll = rand(1,6) + rand(1,6) + $gravityMod;
if($gravityRoll < 2) { $gravityRoll = 2; } if($gravityRoll > 14) {
$gravityRoll = 14;
}
$gravityVal = $gravityArray[$gravityRoll];
if($gravityVal > 10) {
$gravityVal -= 10;
$divide = 1;
}
while($gravityVal > 0) {
$gravityBase += rand(1,6);
$gravityVal–;
}
if($divide) {
$gravity = number_format(1 / $gravityBase, 2);
} else {
$gravity = $gravityBase;
}
$atmoMod = $atmoModArray[$gravityRoll];
return array($gravity, $atmoMod);
}

function atmosphere($atmoMod, $gravity = 1) {
$atmoArray = array(“”, “”, “Atmosphere is escaping the planet”, “Atmosphere is escaping the planet”, “Atmosphere is escaping the planet”, “Extremely thin, no Oxygen”, “Chlorine”, “Carbon Dioxide”, “Nitrogen/Oxygen with heavy gases, Propane, Butane”, “Dense Air (Nitrogen/Oxygen)”, “Nitrogen/Oxygen with Ozone in Stratosphere”, “Nitrogen/Oxygen with trace toxins”, “Ammonia & Methane”, “Hydrogen & Helium”, “Exotic toxic gases”);
$waterModArray = array(0, 0, -6, -6, -6, -6, -4, -3, -2, -1, 1, 0, -4, -5, -6);
$atmosphereRoll = rand(1,6) + rand(1,6) + $atmoMod;
if($atmosphereRoll < 2) { $atmosphereRoll = 2; } if($atmosphereRoll > 14) {
$atmosphereRoll = 14;
}
$atmosphere = $atmoArray[$atmosphereRoll];
$waterMod = $waterModArray[$atmosphereRoll];
$pressure = $atmosphereRoll * $gravity;
return array($atmosphere, $waterMod, $pressure);
}

function water($waterMod) {
$waterArray = array(“”, “”, “No standing water”, “Arid rock/desert world, very little standing water”, “Arid rock/desert world, very little standing water”, “Arid rock/desert world, very little standing water”, “Semi-Arid world, water frozen or beneath surface”, “land”, “land”, “Ocean world”, “Water vapor makes up most of the atmosphere”);
$waterRoll = rand(1,6) + rand(1,6) + $waterMod;
if($waterRoll < 2) { $waterRoll = 2; } if($waterRoll > 10) {
$waterRoll = 10;
}
$water = $waterArray[$waterRoll];
return $water;
}

function climate() {
$climateArray = array(“”, “”, “Frozen solid; ice & rock”, “Frozen solid; ice & rock”, “Arctic conditions”, “Arctic conditions”, “Cold”, “Temperate”, “Hot”, “Greenhouse conditions”, “Greenhouse conditions”, “Wildly variable”, “Hellish”);
$precipDLArray = array(0, 0, 0, 0, 5, 5, 6, 7, 9, 8, 8, 5, 10);
$climateRoll = rand(1,6) + rand(1,6);
if($climateRoll < 2) { $climateRoll = 2; } if($climateRoll > 12) {
$climateRoll = 12;
}
$climate = $climateArray[$climateRoll];
$precipDL = $precipDLArray[$climateRoll];
return array($climate, $precipDL);
}

function biosphere() {
$biosphereArray = array(“”, “”, “Biotoxins in atmosphere”, “Biotoxins in atmosphere”, “No life”, “No life”, “Proto-organisms in suspension”, “Proto-organisms and non-mobile lifeforms”, “Non-sentient lower lifeforms”, “Sentient lifeforms”, “Sentient lifeforms”, “Highly evolved lifeforms”, “Highly evolved lifeforms”);
$biosphereRoll = rand(1,6) + rand(1,6);
$biosphere = $biosphereArray[$biosphereRoll];
return $biosphere;
}

/* BIDNEZ */

$starIndex = 0;
$starType = ‘Star’;
$stars = array();
$planetName = planetName();

$starSizeData = starSize();
/*
$stars[0][‘starSize’] = $starSizeData[0];
$stars[0][‘colorMod’] = $starSizeData[1];
$stars[0][‘planetMod’] = $starSizeData[2];
*/
$starSize = $starSizeData[0];
$colorMod = $starSizeData[1];
$planetMod = $starSizeData[2];

$starColorData = starColor($colorMod, 0); // 1=forcespecial 0=dont
$starColor = $starColorData[0];
$planetCountDice = $starColorData[1];
if($starColor == ‘Special’) {
$starSpecial = specialStar();
$starType = $starSpecial;
switch($starSpecial) {
case ‘Dwarf’ :
$starSize = ‘less than 0.1 times ‘;
$starType = ‘Dwarf Star’;
$starColorData = starColor(0);
$starColor = $starColorData[0];
if($starColor == ‘Special’) {
$starColor = ‘Black’;
}
break;
case ‘Cluster’ :
$starType = ‘Star’;
$starIndex++;
$starColorData = starColor(0);
$starColor = $starColorData[0];
if($starColor == ‘Special’) {
$starSize = ‘- tiny compared to ‘;
$starType = ‘Neutron Star’;
$starColor = ”;
}
break;
case ‘Nova’ :
$starSize = (rand(1,6) * rand(1,6) * 10) . ‘ light-years across’;
$starColor = ”;
break;
case ‘Brown Dwarf Star’ :
case ‘Pulsar’ :
case ‘Quasar’ :
case ‘Black Hole’ :
$starSize = ‘- tiny compared to ‘;
$starColor = ”;
break;
default :
$starType = ‘Star’;
break;
}
}
$stars[0][‘starSize’] = $starSize;
$stars[0][‘starType’] = $starType;
$stars[0][‘starColor’] = $starColor;

if($starIndex) {
while($starIndex > 0) {
$starSizeData = starSize();
$starSize = $starSizeData[0];
$colorMod = $starSizeData[1];
$planetMod = $starSizeData[2];
$starColorData = starColor($colorMod);
$starColor = $starColorData[0];
// $planetCountDice = $starColorData[1];
if($starColor == ‘Special’) {
$starSpecial = specialStar();
$starType = $starSpecial;
switch($starSpecial) {
case ‘Dwarf’ :
$starSize = ‘less than 0.1 times ‘;
$starType = ‘Dwarf Star’;
$starColorData = starColor(0);
$starColor = $starColorData[0];
if($starColor == ‘Special’) {
$starColor = ‘Black’;
}
break;
case ‘Cluster’ :
$starType = ‘Star’;
$starIndex++;
$starColorData = starColor(0);
$starColor = $starColorData[0];
if($starColor == ‘Special’) {
$starSize = ‘- tiny compared to ‘;
$starType = ‘Neutron Star’;
$starColor = ”;
}
break;
case ‘Nova’ :
$starSize = (rand(1,6) * rand(1,6) * 10) . ‘ light-years across’;
$starColor = ”;
break;
case ‘Brown Dwarf Star’ :
case ‘Pulsar’ :
case ‘Quasar’ :
case ‘Black Hole’ :
$starSize = ‘- tiny compared to ‘;
$starColor = ”;
break;
default :
$starType = ‘Star’;
break;
}
}
$stars[$starIndex][‘starSize’] = $starSize;
$stars[$starIndex][‘starType’] = $starType;
$stars[$starIndex][‘starColor’] = $starColor;
$starIndex–;
}
}

$planetCount = planetCount($planetCountDice);
$romanArray = array(”, ‘I’, ‘II’, ‘III’, ‘IV’, ‘V’, ‘VI’, ‘VII’, ‘VIII’, ‘IX’, ‘X’, ‘XI’, ‘XII’, ‘XIII’, ‘XIV’, ‘XV’, ‘XVI’, ‘XVII’, ‘XVIII’);
$planetNumber = rand(1,$planetCount);
$romanNumber = $romanArray[$planetNumber];

$planetSizeData = planetSize($planetMod);
$planetSize = $planetSizeData[0];
$gravityMod = $planetSizeData[1];

$gravityData = gravity($gravityMod);
$gravity = $gravityData[0];
$atmoMod = $gravityData[1];

$atmosphereData = atmosphere($atmoMod, $gravity);
$atmosphere = $atmosphereData[0];
$waterMod = $atmosphereData[1];
$pressure = $atmosphereData[2];

$water = water($waterMod);
if($water == ‘land’) {
$watercover = (rand(1,6)+3)*10;
$landcover = 100 – $watercover;
$water = $landcover . ‘% land, ‘ . $watercover . ‘% water’;
}

$climateData = climate();
$climate = $climateData[0];
$precipDL = $climateData[1];

$biosphere = biosphere();

/* DISPLAY */

echo ‘STELLAR SYSTEM ‘ . strtoupper($planetName) . ‘
‘;
$i = 1;
switch(count($stars)) {
case 5 :
echo ‘Pentary System:’;
break;
case 4 :
echo ‘Quadrary System:’;
break;
case 3 :
echo ‘Trinary System:’;
break;
case 2 :
echo ‘Binary System:’;
break;
default :
break;
}
foreach($stars AS $thing) {
if(count($stars) > 1) {
echo ‘
‘ . $i . ‘. ‘;
}
if($thing[‘starColor’] AND $thing[‘starColor’] == ‘Orange’) {
echo ‘An ‘;
} else {
echo ‘A ‘;
}
if($thing[‘starColor’]) {
echo $thing[‘starColor’] . ‘ ‘;
}
echo $thing[‘starType’] . ‘ ‘;
echo $thing[‘starSize’];
if($thing[‘starType’] != ‘Nova’) {
echo ‘the size of Sol’;
}
$i++;
}
echo ‘
‘;
echo ‘with ‘ . $planetCount;
if($planetCount == 1) {
echo ‘ planet in orbit.
‘;
} else {
echo ‘ planets in orbit.
‘;
}
echo ‘
‘ . strtoupper($planetName) . ‘ ‘ . $romanNumber . ‘
‘;
echo ‘TYPE: ‘ . $planetSize . ‘
‘;
echo ‘GRAVITY: ‘ . $gravity . ‘ G
‘;
echo ‘ATMOSPHERE: ‘ . $atmosphere . ‘
‘;
echo ‘PRESSURE: ‘ . $pressure . ‘ Earth atmospheres
‘;
if($planetSize != ‘Gas Giant’) {
echo ‘WATER: ‘ . $water . ‘
‘;
}
echo ‘CLIMATE: ‘ . $climate . ‘
‘;
echo ‘PRECIP DL: ‘ . $precipDL . ‘
‘;
echo ‘BIOSPHERE: ‘ . $biosphere . ‘
‘;

?>


‘;
?>

DayTrippers is a Surreal Science Fiction Reality-Hopping OSR RPG. Now available at RPGnow.com.

Explore More Insights

Alfred Jarry

"We shall not have succeeded in demolishing everything unless we demolish the ruins as well. But the only way I can see of doing that is to use them to put up a lot of fine, well-designed buildings." Field: Playwrite, Artist, Pataphysicist.Born: 1873.Background: The...

read more

Andy Kaufman

"Pure entertainment is not an egotistical lady singing boring songs onstage for two hours and people in tuxes clapping whether they like it or not. It's the real performers on the street who can hold people's attention and keep them from walking away." Field:...

read more

Bill Hicks

"The world is like a ride in an amusement park... Some people have been on the ride for a long time and they begin to question, "Is this real, or is this just a ride?" And other people have remembered, and they come back to us, they say, 'Hey - don't worry,...

read more