in.css

/**
 * General hiding of elements
 **/
._in .Wm, /* Message list count */
._in .aeN .z0 > .L3::before, /* Compose Icon */ 
._in .aeG, /* Footer stats */ 
._in .gb_Be img.gb_Wa, /* Gmail logo */
._in .gb_Ra .gb_Sa /* GSuite Logo */
{
  display: none !important;
}

/**
 * Body and base
 **/

body._in,
._in .n0,
._in .Wn,
._in .zA > .a4W {
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif !important;
}

body._in,
._in .no {
  background: #f2f2f2;
}

._in .aeJ /* Middle section */,
._in .brC-aT5-aOt-Jw /* Right Sidebar */{
  background: transparent !important;
  padding: 0 5px;
}


/**
 * Toolbar / Header
 **/

/* Toolbar background */
._in header { background-color: #898984 !important; }
._in[data-hash*="#inbox"] header { background-color: #4285f4 !important; }
._in[data-hash*="#starred"] header { background-color: #FDB500 !important; }
._in[data-hash*="#snoozed"] header { background-color: #ef6c00 !important; }
._in[data-hash*="#search/-is%3Ainbox"] header { background-color: #0f9d58 !important; }

/* Toolbar shadow */
._in header:before {
    box-shadow: 0 0 4px rgba(0,0,0,.14), 0 4px 8px rgba(0,0,0,.28);
    content: "";
    height: 64px;
    left: -2%;
    position: fixed;
    width: 104%;
    pointer-events: none;
}

/* Toolbar icons */
._in header svg {
  color: #fff !important;
  opacity: 1 !important;
}

/* Toolbar title */

._inTitle {
  display: none;
}

._in ._inTitle {
  color: #fff;
  display: block;
  font-family: "Helvetica Neue", Helvetica, Arial, sans-serif !important;
  font-size: 1.5em;
  margin: -7px 0 0 8px;
  -webkit-font-smoothing: antialiased;
}

._in a.gb_Je {
  margin-top: -4px;
  display: block;
  -webkit-font-smoothing: antialiased;
  color: #fff;
  text-decoration: none;
  font-size: 20px;
}

/* Toolbar left column (inbox title) */
._in .gb_Fe {
  position: absolute !important;
  left: 8px !important;
  top: 8px !important;
}

/* Toolbar form */
._in form#aso_search_form_anchor {
  width: 1200px;
  max-width: unset;
  border-radius: 2px !important;
  background: rgba(255, 255, 255, .15) !important;
  margin: 0 auto !important;
}

@media (max-width: 1632px) {
  ._in form#aso_search_form_anchor {
    max-width: 100% !important;
    width: auto;
  }
}

@media (max-width: 990px) {
  ._in form#aso_search_form_anchor {
    max-width: 100% !important;
    width: auto;
  }
}

/* Toolbar input field */
._in input[name="q"] {
  filter: invert(100%);
}

/* Toolbar right column (avatar icon) */
.gb_jb.gb_Cc {
  position: absolute !important;
  right: 8px !important;
  top: 8px !important;
}

@media (max-width: 1800px) {
  ._in .gb_Se {
    width: 66.66%;
  }
}

@media (max-width: 1632px) {
  ._in .gb_Se {
    width: auto !important;
    margin-left: 272px !important;
    margin-right: 180px !important;
  }
}


/* GSuite button, invert back */
._in .gb_Ra {
  border: 0 !important;
  width: auto !important;
  background-color: transparent !important;
} 

/**
 * Sidebar
 **/

._in .aim {
  padding-left: 4px !important;
}

/* Menu item row */
._in .TK .TO {
  border-radius: 2px !important;
}

/* Menu item row, hover */
._in .TK .TO:hover {
  background-color: rgba(0,0,0,.05) !important;
  cursor: pointer;
}

/* Menu item row active */
._in .TK .TO:active,
._in .n6 .ah9.aiu:active
._in .CL:active,
._in .TO.nZ,
._in .TO.NQ,
._in .TO.ol {
  background-color: rgba(0,0,0,.05) !important; 
}

/* Left sidebar collapsed */
._in .aeN.bhZ {
  display: none !important;
}

/* Menu container */
._in .aeN {
  width: 232px !important;
  max-width: unset !important;
  min-width: unset !important;
  left: 0;
}
._in .wT {
  padding-top: 4px;
  max-width: unset;
  min-width: unset;
  width: 224px;
  padding: 12px 8px 52px;
}

/* Menu item sections */
._in .TK {
    border-bottom: 1px solid #ddd;
    padding: 8px 0;
}

/* Menu item row inner */
._in .aim .TN {
  height: 40px;
}

/* Menu item link */
._in .TO .nU > .n0 {
  font-size: 14px;
  font-weight: normal;
}

/* Resetting Inbox menu item custom styling */
._in .wT > .n3 .byl:first-child .aim:first-child .nZ {
  background-color: rgba(0,0,0,.05) !important; 
}
.qj {
  width: 24px !important;
  height: 24px !important;
  opacity: 1 !important;
  margin-right: 24px !important;
  background-size: 24px !important;
}
.qj::before {
  content: none !important;
}
.qj::after {
  content: none !important;
}
/* Inbox */
._in .aHS-bnt .qj {
  background-image: url("//www.gstatic.com/images/icons/material/system/2x/inbox_googblue_24dp.png") !important;
}
/* Dropdown arrow */
._in .aHS-bnt .afM {
  background-image: url('//www.gstatic.com/images/icons/material/system/2x/arrow_drop_down_black_20dp.png') !important;
}
/* Starred, Important, Chats */
._in .aHS-bnw .qr,
._in .aHS-bns .qr,
._in .aHS-aHP .qr {
  opacity: 0.6 !important;
}
/* Starred */
._in .aHS-bnw .qj {
  background-image: url("//www.gstatic.com/images/icons/material/system/2x/grade_black_24dp.png") !important;
}
/* Important */
._in .aHS-bns .qj {
  background-image: url("//www.gstatic.com/images/icons/material/system/2x/label_important_black_24dp.png") !important;
}
/* Chats */
._in .aHS-aHP .qj {
  background-image: url("//www.gstatic.com/images/icons/material/system/2x/hangout_black_24dp.png") !important;
}
/* Snoozed */
._in .aHS-bu1 .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_upcoming_clr_24dp_r5_2x.png") !important;
}
/* Sent */
._in .aHS-bnu .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_sent_right_g60_24dp_r1_2x.png") !important;
}
/* Drafts */
._in .aHS-bnq .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_draft_g60_24dp_r2_2x.png") !important;
}
/* Trash */
._in .aHS-bnx .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_trash_g60_24dp_r2_2x.png") !important;
}
/* Category */
._in .aHS-bnr .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_custom-cluster_24px_g60_r3_2x.png") !important;
}
/* Done */
._in .aHS-aHO .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_done_clr_24dp_r4_2x.png") !important;
}
/* Spam */
._in .aHS-bnv .qj {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_spam_g60_24dp_r2_2x.png") !important;
}
.TO.nZ .n0 {
  color: #212121 !important;
  outline: none;
}
.TO .n0 {
  color: #616161 !important;
  outline: none;
}

/**
 * Center message list section
 **/
.bkL .no {
  position: relative !important;
}
._in .aeN {
  position: absolute !important;
}
._in .bhZ+.bkK {
  margin-left: auto !important;
}
._in .bkK {
  width: 1200px !important;
  margin: 0 auto;
}
._in .bAw {
  position: absolute !important;
  right: 0 !important;
  top: 0 !important;
}

@media (max-width: 1800px) {
  ._in .bkK {
    width: 66.66%;
  }
}

@media (max-width: 1632px) {
  ._in .bkK {
    min-width: 512px;
    margin-left: 272px;
    margin-right: 55px;
  }
}

/* Section */
._in .aDM {
  margin-bottom: 0px;
}


/* Section collapse chevron */
._in h3.Wr > img {
  display: none;
}

/* Section wrapper */
._in h3.Wr {
  margin-left: 0;
}

/* Section title */
._in h3.Wr > .Wn {
  font-size: 13px;
  -webkit-font-smoothing: auto;
  line-height: 24px;
  letter-spacing: normal;
  font-weight: normal;
  color: #616161;
 }

 /* Custom Sweep Button */
 ._inSweep {
  background: transparent url("//www.gstatic.com/images/icons/material/system/1x/sweep_black_24dp.png") !important;
  width: 24px;
  height: 24px;
  opacity: 0.6;
  border: 0;
  box-sizing: border-box;
  display: none;
  outline: 0;
  cursor: pointer;
 }

 ._in ._inSweep {
  display: inline-block;
 }

 ._inSweep:hover {
  opacity: 1;
 }

 /* Section wrapper */
._in .UI {
  padding: 20px 0;
}

/* Section row list table */
._in .UI[gh="tl"] table {
  box-shadow: 0 -1px 0 #e0e0e0, 0 0 2px rgba(0,0,0,.12), 0 2px 4px rgba(0,0,0,.24);
}
._in .UI table {
  box-shadow: none;
}

 /* Message row */
._in .zE,
._in .yO {
  background: #fff !important;
}

/* Message row */
._in .zA {
  padding-top: 12px;
  padding-bottom: 13px;
}

/* Archive button */
._in .brq {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/1x/btw_ic_done_black_24dp.png");
}
._in .brq.pW {
  background-image: url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/2x/ic_mark-done_clr_24dp_r4_2x.png");
}
.pW {
  opacity: 1 !important;
}

/**
 * Other elements 
 **/

/* Compose button wrapper */
._in .aeN .z0 {
  height: auto;
  margin: 0;
}

/* Compose button */
._in .aeN .z0 > .L3 {
  background: #d23f31 url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/1x/btw_ic_speeddial_white_24dp.png") no-repeat center center;
  height: 56px;
  width: 56px;
  border-radius:50%;
  box-shadow: 0 0 4px rgba(0,0,0,.14), 0 4px 8px rgba(0,0,0,.28);
  position: fixed;
  right: 15px;
  bottom: 15px;
  z-index: 100;
  text-indent: -9999px;
  overflow: hidden;
  padding: 0;
}
._in .aeN .z0 > .L3:hover {
  background: #d23f31 url("//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/1x/btw_ic_speeddial_compose_white_24dp.png") no-repeat center center;
}

/* Debug element */
._in::after {
  position: fixed;
  bottom: 25px;
  left: 0;
  z-index: 9999;
  background: rgba(0,0,0,0.3);
  color: #fff;
  font-family: monospace;
  font-size: 14;
}

/* Mail highlight bar */
.zA>.PE.PF::before {
  left: -1px;
}

/* Empty Appearance */
.TD>.TC {
  background-image: url('//ssl.gstatic.com/bt/C3341AA7A1A076756462EE2E5CD71C11/zero/2x/ic_zero_inbox_2x.png');
  background-repeat: no-repeat;
  background-position: center;
  height: 500px;
  color: transparent;
}