Custom styles for Gmail (based on https://userstyles.org/styles/111817/gmail-with-inbox-color-scheme)

styles.css

* {
  font-family: 'Roboto', sans-serif !important;
}

html {
  font-size: 100%;
  line-height: 1.4;
}

.qp {
  border-bottom: 0;
}

.asT-asx {
  width: 0;
  height: 0;
  border-style: solid;
  border-width: 5px 3.5px 0 3.5px;
  border-color: #4285F4 transparent transparent transparent;
}

.aiw .qp {
  margin-bottom: 0 !important;
}

.gb_Ib {
  display: none !important;
}

.gb_9a {
  display: none !important;
}

.w-asV {
  margin: 0 !important;
}

.aeN {
  z-index: 3;
}

.gb_ve>.gb_R,
.gb_ue>.gb_R,
.gb_cb,
.gb_2d,
.gb_Re,
.gb_1d,
.gb_Td {
  height: 40px !important;
}

.gb_Td>.gb_R {
  height: 40px;
  line-height: 38px;
}

#gb > div,
.gb_de,
.gb_ce,
#gba {
  height: 40px;
}

#gbq2 {
  padding-top: 4px;
}

.aeG {
  display: none;
}

.aki.pp {
  display: none;
  visibility: hidden;
}

.aj9.pp {
  position: relative;
  background: white;
}

.n4 {
  padding-top: 4px;
  padding-bottom: 4px;
}

.TN {
  padding-top: 4px;
  padding-bottom: 4px;
}

.TB {
  margin-top: 10px;
}

.xY.apy {
  padding-top: 4px !important;
}

.xY.apA {
  padding-bottom: 4px !important;
}

.TC {
  padding: 20px;
  background: rgba(0, 0, 0, 0.025);
  color: rgba(0, 0, 0, 0.25);
}

.xY {
  padding-top: 6px;
  padding-bottom: 6px;    
}

.apO {
  display: none;
}

.md {
  display: none;
}

.G-atb {
  border-bottom: 0 !important;
  -webkit-box-shadow: none !important;
}

.gb_3b, .T-I-KE {
  background: #4285F4 !important;
}

.gb_3b {
  box-shadow: 0 0 2px rgba(0,0,0,.14),0 2px 4px rgba(0,0,0,.28);
}

.gb_3b::before {
  display: none;
}

.gb_Xa .gb_0a {
  background-position: 0 -148px !important;
  height: 38px !important;
  width: 104px !important;
}

#gb#gb a.gb_k, #gb#gb a.gb_l {
  color: #FFF !important;
}

.T-I-KE:hover {
  background: #3571DF;
  border-color: #3571DF;
}

.akh, .ake, .nZ .nU, .nZ .n0 {
  color: #4285f4 !important;
}

.ain {
  border-left-color: #4285f4;
}

#gbqfqw {
  background: rgba(255,255,255,.15);
  border: 0;
  border-radius: 2px;
}

#gbqfqw.gsfe_a {
  background: rgba(255,255,255,.3);
}

#gbqfqw.gsfe_b {
  background: #fff;
}

#gbqfqw .gbqfif {
  color: rgba(0, 0, 0, 0.25);
}

#gbqfqw.gsfe_b .gbqfif {
  color: #222;
}

#gbqfbw {
  display: none;
}

.ma {
  display: none;
}

div.TH {
  top: 4px !important;
}

.gb_kb,
.gb_jb,
.gb_zc,
.gb_xc,
.gb_ib,
.gb_hc,
#gbq1,
.gb_Nb,
.gb_Kb,
.gb_Lb,
.gb_bb {
  display: none !important;
}

.gb_8a {
  width: 20px;
  height: 20px;
  background-size: 20px 20px;
}

.gb_db.gb_R {
  display: flex;
  align-items: center;
}

.gb_uf > .gb_R {
    height: 40px;
    align-items: center;
}

#gb#gb a.gb_b {
    display: flex;
    align-items: center;
}

.gb_T .gb_tg {
   align-items: center;   
}