script.js

let brain = document.querySelector('.brain-cost')
let parsedBrain = parseFloat(brain.innerHTML)

let clickerCost = document.querySelector('.clicker-cost')
let parsedClickerCost = parseFloat(clickerCost.innerHTML)
let clickerLevel = document.querySelector('.clicker-level')
let clickerIncrease = document.querySelector('.clicker-increase')
let parsedCLickerIncrease = parseFloat(clickerIncrease.innerHTML)

let bookCost = document.querySelector('.book-cost')
let parsedBookCost = parseFloat(bookCost.innerHTML)
let bookLevel = document.querySelector('.book-level')
let bookIncrease = document.querySelector('.book-increase')
let parsedBookIncrease = parseFloat(bookIncrease.innerHTML)

let schoolCost = document.querySelector('.school-cost')
let parsedSchoolCost = parseFloat(schoolCost.innerHTML)
let schoolLevel = document.querySelector('.school-level')
let schoolIncrease = document.querySelector('.school-increase')
let parsedSchoolIncrease = parseFloat(schoolIncrease.innerHTML)

let ipcText = document.getElementById("ipc-text")
let ipsText = document.getElementById("ips-text")

let ipc = 1;

let ips = 0;

function incrementBrain() {
    brain.innerHTML = Math.round(parsedBrain += ipc);
}

function buyClicker() {
    if (parsedBrain >= parsedClickerCost) {
        brain.innerHTML = Math.round(parsedBrain -= parsedClickerCost);

        clickerLevel.innerHTML++

        parsedCLickerIncrease = parseFloat((parsedCLickerIncrease * 1.03).toFixed(2))
        clickerIncrease.innerHTML = parsedCLickerIncrease
        ipc += parsedCLickerIncrease

        parsedClickerCost *= 1.18;
        clickerCost.innerHTML = Math.round(parsedClickerCost)
    }
}

function buyBook() {
    if (parsedBrain >= parsedBookCost) {
        brain.innerHTML = Math.round(parsedBrain -= parsedBookCost);

        bookLevel.innerHTML++

        parsedBookIncrease = parseFloat((parsedBookIncrease * 1.03).toFixed(2))
        bookIncrease.innerHTML = parsedBookIncrease
        ips += parsedBookIncrease

        parsedBookCost *= 1.18;
        bookCost.innerHTML = Math.round(parsedBookCost)
    }
}

function buySchool() {
    if (parsedBrain >= parsedSchoolCost) {
        brain.innerHTML = Math.round(parsedBrain -= parsedSchoolCost);

        schoolLevel.innerHTML++

        parsedSchoolIncrease = parseFloat((parsedSchoolIncrease * 1.03).toFixed(2))
        schoolIncrease.innerHTML = parsedSchoolIncrease
        ips += parsedSchoolIncrease

        parsedSchoolCost *= 1.18;
        schoolCost.innerHTML = Math.round(parsedSchoolCost)
    }
}

setInterval(() => {
    parsedBrain += ips
    brain.innerHTML = Math.round(parsedBrain)
    ipcText.innerHTML = Math.round(ipc)
    ipsText.innerHTML = Math.round(ips);
}, 1000)