const canvas = document.getElementById('matrix-canvas');
const ctx = canvas.getContext('2d');

canvas.width = window.innerWidth;
canvas.height = window.innerHeight;

const letters = 'ABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZABCDEFGHIJKLMNOPQRSTUVXYZ1234567890';
const fontSize = 16;
let columns = canvas.width / fontSize;

const drops = [];
for (let x = 0; x < columns; x++) {
    drops[x] = 1;
}

function draw() {
    ctx.fillStyle = 'rgba(0, 0, 0, 0.05)';
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    ctx.fillStyle = '#0F0'; // green text
    ctx.font = fontSize + 'px arial';

    for (let i = 0; i < drops.length; i++) {
        const text = letters.charAt(Math.floor(Math.random() * letters.length));
        ctx.fillText(text, i * fontSize, drops[i] * fontSize);

        if (drops[i] * fontSize > canvas.height && Math.random() > 0.975) {
            drops[i] = 0;
        }
        drops[i]++;
    }
}

setInterval(draw, 33);

window.addEventListener('resize', () => {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;
    columns = canvas.width / fontSize;
    drops.length = 0;
    for (let x = 0; x < columns; x++) {
        drops[x] = 1;
    }
});