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.

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